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The Descent of Man and Selection in Relation to Sex
by Charles Darwin
August 2000 [Etext #2300]
The Project Gutenberg Etext The Descent of Man by Charles Darwin
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THE DESCENT OF MAN
AND
SELECTION IN RELATION TO SEX
Works by Charles Darwin, F.R.S.
Life and Letters of Charles Darwin. With an Autobiographical Chapter.
Edited by Francis Darwin. Portraits. 3 volumes 36s. Popular Edition.
Condensed in 1 volume 7s 6d.
Naturalist's Journal of Researches into the Natural History and Geology of
Countries Visited during a Voyage Round the World. With 100 Illustrations
by Pritchett. 21s. Popular Edition. Woodcuts. 3s 6d. Cheaper Edition,
2s. 6d. net.
Origin of Species by means of Natural Selection; or, The Preservation of
Favoured Races in the Struggle for Life. Large Type Edition, 2 volumes
12s. Popular Edition, 6s. Cheaper Edition with Portrait, 2s. 6d.
Various Contrivances by which Orchids are Fertilized by Insects. Woodcuts.
7s. 6d.
Variation of Animals and Plants under Domestication. Illustrations. 15s.
Descent of Man, and Selection in relation to Sex. Illustrations. Large
Type Edition, 2 volumes 15s. Popular Edition, 7s 6d. Cheaper Edition, 2s.
6d. net.
Expression of the Emotions in Man and Animals. Illustrations. 12s.
Insectivorous Plants. Illustrations. 9s.
Movements and Habits of Climbing Plants. Woodcuts. 6s.
Cross and Self-Fertilization in the Vegetable Kingdom. Illustrations. 9s.
Different Forms of Flowers on Plants of the Same Species. Illustrations.
7s. 6d.
Formation of Vegetable Mould through the Action of Worms. Woodcuts. 6s.
The above works are Published by John Murray.
Structure and Distribution of Coral Reefs. Smith, Elder, & Co.
Geological Observations on Volcanic Islands and Parts of South America.
Smith, Elder, & Co.
Monograph of the Cirripedia. Illustrations. 2 volumes. 8vo. Ray
Society.
Monograph of the Fossil Lepadidae, or Pedunculated Cirripedes of Great
Britain. Palaeontographical Society.
Monograph of the Fossil Balanidae and Verrucidae of Great Britain.
Palaeontographical Society.
THE DESCENT OF MAN
AND
SELECTION IN RELATION TO SEX
BY
CHARLES DARWIN, M.A., F.R.S.
Uniform with this Volume
The Origin of Species, by means of Natural Selection; or, The Preservation
of Favoured Races in the Struggle for Life. Popular Edition, with a
Photogravure Portrait. Large Crown 8vo. 2s. 6d. net.
A Naturalist's Voyage. Journal of Researches into the Natural History and
Geology of the Countries visited during the Voyage of H.M.S. "Beagle" round
the World, under the Command of Capt. Fitz Roy, R.N. Popular Edition, with
many Illustrations. Large Crown 8vo. 2s. 6d. net.
PREFACE TO THE SECOND EDITION.
During the successive reprints of the first edition of this work, published
in 1871, I was able to introduce several important corrections; and now
that more time has elapsed, I have endeavoured to profit by the fiery
ordeal through which the book has passed, and have taken advantage of all
the criticisms which seem to me sound. I am also greatly indebted to a
large number of correspondents for the communication of a surprising number
of new facts and remarks. These have been so numerous, that I have been
able to use only the more important ones; and of these, as well as of the
more important corrections, I will append a list. Some new illustrations
have been introduced, and four of the old drawings have been replaced by
better ones, done from life by Mr. T.W. Wood. I must especially call
attention to some observations which I owe to the kindness of Prof. Huxley
(given as a supplement at the end of Part I.), on the nature of the
differences between the brains of man and the higher apes. I have been
particularly glad to give these observations, because during the last few
years several memoirs on the subject have appeared on the Continent, and
their importance has been, in some cases, greatly exaggerated by popular
writers.
I may take this opportunity of remarking that my critics frequently assume
that I attribute all changes of corporeal structure and mental power
exclusively to the natural selection of such variations as are often called
spontaneous; whereas, even in the first edition of the 'Origin of Species,'
I distinctly stated that great weight must be attributed to the inherited
effects of use and disuse, with respect both to the body and mind. I also
attributed some amount of modification to the direct and prolonged action
of changed conditions of life. Some allowance, too, must be made for
occasional reversions of structure; nor must we forget what I have called
"correlated" growth, meaning, thereby, that various parts of the
organisation are in some unknown manner so connected, that when one part
varies, so do others; and if variations in the one are accumulated by
selection, other parts will be modified. Again, it has been said by
several critics, that when I found that many details of structure in man
could not be explained through natural selection, I invented sexual
selection; I gave, however, a tolerably clear sketch of this principle in
the first edition of the 'Origin of Species,' and I there stated that it
was applicable to man. This subject of sexual selection has been treated
at full length in the present work, simply because an opportunity was here
first afforded me. I have been struck with the likeness of many of the
half-favourable criticisms on sexual selection, with those which appeared
at first on natural selection; such as, that it would explain some few
details, but certainly was not applicable to the extent to which I have
employed it. My conviction of the power of sexual selection remains
unshaken; but it is probable, or almost certain, that several of my
conclusions will hereafter be found erroneous; this can hardly fail to be
the case in the first treatment of a subject. When naturalists have become
familiar with the idea of sexual selection, it will, as I believe, be much
more largely accepted; and it has already been fully and favourably
received by several capable judges.
DOWN, BECKENHAM, KENT,
September, 1874.
First Edition February 24, 1871.
Second Edition September, 1874.
CONTENTS.
INTRODUCTION.
PART I. THE DESCENT OR ORIGIN OF MAN.
CHAPTER I.
The Evidence of the Descent of Man from some Lower Form.
Nature of the evidence bearing on the origin of man--Homologous structures
in man and the lower animals--Miscellaneous points of correspondence--
Development--Rudimentary structures, muscles, sense-organs, hair, bones,
reproductive organs, etc.--The bearing of these three great classes of
facts on the origin of man.
CHAPTER II.
On the Manner of Development of Man from some Lower Form.
Variability of body and mind in man--Inheritance--Causes of variability--
Laws of variation the same in man as in the lower animals--Direct action of
the conditions of life--Effects of the increased use and disuse of parts--
Arrested development--Reversion--Correlated variation--Rate of increase--
Checks to increase--Natural selection--Man the most dominant animal in the
world--Importance of his corporeal structure--The causes which have led to
his becoming erect--Consequent changes of structure--Decrease in size of
the canine teeth--Increased size and altered shape of the skull--Nakedness
--Absence of a tail--Defenceless condition of man.
CHAPTER III.
Comparison of the Mental Powers of Man and the Lower Animals.
The difference in mental power between the highest ape and the lowest
savage, immense--Certain instincts in common--The emotions--Curiosity--
Imitation--Attention--Memory--Imagination--Reason--Progressive improvement
--Tools and weapons used by animals--Abstraction, Self-consciousness--
Language--Sense of beauty--Belief in God, spiritual agencies,
superstitions.
CHAPTER IV.
Comparison of the Mental Powers of Man and the Lower Animals--continued.
The moral sense--Fundamental proposition--The qualities of social animals--
Origin of sociability--Struggle between opposed instincts--Man a social
animal--The more enduring social instincts conquer other less persistent
instincts--The social virtues alone regarded by savages--The self-regarding
virtues acquired at a later stage of development--The importance of the
judgment of the members of the same community on conduct--Transmission of
moral tendencies--Summary.
CHAPTER V.
On the Development of the Intellectual and Moral Faculties during Primeval
and Civilised times.
Advancement of the intellectual powers through natural selection--
Importance of imitation--Social and moral faculties--Their development
within the limits of the same tribe--Natural selection as affecting
civilised nations--Evidence that civilised nations were once barbarous.
CHAPTER VI.
On the Affinities and Genealogy of Man.
Position of man in the animal series--The natural system genealogical--
Adaptive characters of slight value--Various small points of resemblance
between man and the Quadrumana--Rank of man in the natural system--
Birthplace and antiquity of man--Absence of fossil connecting-links--Lower
stages in the genealogy of man, as inferred firstly from his affinities and
secondly from his structure--Early androgynous condition of the Vertebrata
--Conclusion.
CHAPTER VII.
On the Races of Man.
The nature and value of specific characters--Application to the races of
man--Arguments in favour of, and opposed to, ranking the so-called races of
man as distinct species--Sub-species--Monogenists and polygenists--
Convergence of character--Numerous points of resemblance in body and mind
between the most distinct races of man--The state of man when he first
spread over the earth--Each race not descended from a single pair--The
extinction of races--The formation of races--The effects of crossing--
Slight influence of the direct action of the conditions of life--Slight or
no influence of natural selection--Sexual selection.
PART II. SEXUAL SELECTION.
CHAPTER VIII.
Principles of Sexual Selection.
Secondary sexual characters--Sexual selection--Manner of action--Excess of
males--Polygamy--The male alone generally modified through sexual
selection--Eagerness of the male--Variability of the male--Choice exerted
by the female--Sexual compared with natural selection--Inheritance at
corresponding periods of life, at corresponding seasons of the year, and as
limited by sex--Relations between the several forms of inheritance--Causes
why one sex and the young are not modified through sexual selection--
Supplement on the proportional numbers of the two sexes throughout the
animal kingdom-- The proportion of the sexes in relation to natural
selection.
CHAPTER IX.
Secondary Sexual Characters in the Lower Classes of the Animal Kingdom.
These characters are absent in the lowest classes--Brilliant colours--
Mollusca--Annelids--Crustacea, secondary sexual characters strongly
developed; dimorphism; colour; characters not acquired before maturity--
Spiders, sexual colours of; stridulation by the males--Myriapoda.
CHAPTER X.
Secondary Sexual Characters of Insects.
Diversified structures possessed by the males for seizing the females--
Differences between the sexes, of which the meaning is not understood--
Difference in size between the sexes--Thysanura--Diptera--Hemiptera--
Homoptera, musical powers possessed by the males alone--Orthoptera, musical
instruments of the males, much diversified in structure; pugnacity;
colours--Neuroptera, sexual differences in colour--Hymenoptera, pugnacity
and odours--Coleoptera, colours; furnished with great horns, apparently as
an ornament; battles; stridulating organs generally common to both sexes.
CHAPTER XI.
Insects, continued.--Order Lepidoptera.
(Butterflies and Moths.)
Courtship of Butterflies--Battles--Ticking noise--Colours common to both
sexes, or more brilliant in the males--Examples--Not due to the direct
action of the conditions of life--Colours adapted for protection--Colours
of moths--Display--Perceptive powers of the Lepidoptera--Variability--
Causes of the difference in colour between the males and females--Mimicry,
female butterflies more brilliantly coloured than the males--Bright colours
of caterpillars--Summary and concluding remarks on the secondary sexual
character of insects--Birds and insects compared.
CHAPTER XII.
Secondary Sexual Characters of Fishes, Amphibians, and Reptiles.
Fishes: Courtship and battles of the males--Larger size of the females--
Males, bright colours and ornamental appendages; other strange characters--
Colours and appendages acquired by the males during the breeding-season
alone--Fishes with both sexes brilliantly coloured--Protective colours--The
less conspicuous colours of the female cannot be accounted for on the
principle of protection--Male fishes building nests, and taking charge of
the ova and young. AMPHIBIANS: Differences in structure and colour
between the sexes--Vocal organs. REPTILES: Chelonians--Crocodiles--
Snakes, colours in some cases protective--Lizards, battles of--Ornamental
appendages--Strange differences in structure between the sexes--Colours--
Sexual differences almost as great as with birds.
CHAPTER XIII.
Secondary Sexual Characters of Birds.
Sexual differences--Law of battle--Special weapons--Vocal organs--
Instrumental music--Love-antics and dances--Decorations, permanent and
seasonal--Double and single annual moults--Display of ornaments by the
males.
CHAPTER XIV.
Birds--continued.
Choice exerted by the female--Length of courtship--Unpaired birds--Mental
qualities and taste for the beautiful--Preference or antipathy shewn by the
female for particular males--Variability of birds--Variations sometimes
abrupt--Laws of variation--Formation of ocelli--Gradations of character--
Case of Peacock, Argus pheasant, and Urosticte.
CHAPTER XV.
Birds--continued.
Discussion as to why the males alone of some species, and both sexes of
others are brightly coloured--On sexually-limited inheritance, as applied
to various structures and to brightly-coloured plumage--Nidification in
relation to colour--Loss of nuptial plumage during the winter.
CHAPTER XVI.
Birds--concluded.
The immature plumage in relation to the character of the plumage in both
sexes when adult--Six classes of cases--Sexual differences between the
males of closely-allied or representative species--The female assuming the
characters of the male--Plumage of the young in relation to the summer and
winter plumage of the adults--On the increase of beauty in the birds of the
world--Protective colouring--Conspicuously coloured birds--Novelty
appreciated--Summary of the four chapters on birds.
CHAPTER XVII.
Secondary Sexual Characters of Mammals.
The law of battle--Special weapons, confined to the males--Cause of absence
of weapons in the female--Weapons common to both sexes, yet primarily
acquired by the male--Other uses of such weapons--Their high importance--
Greater size of the male--Means of defence--On the preference shewn by
either sex in the pairing of quadrupeds.
CHAPTER XVIII.
Secondary Sexual Characters of Mammals--continued.
Voice--Remarkable sexual peculiarities in seals--Odour--Development of the
hair--Colour of the hair and skin--Anomalous case of the female being more
ornamented than the male--Colour and ornaments due to sexual selection--
Colour acquired for the sake of protection--Colour, though common to both
sexes, often due to sexual selection--On the disappearance of spots and
stripes in adult quadrupeds--On the colours and ornaments of the
Quadrumana--Summary.
PART III. SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.
CHAPTER XIX.
Secondary Sexual Characters of Man.
Differences between man and woman--Causes of such differences, and of
certain characters common to both sexes--Law of battle--Differences in
mental powers, and voice--On the influence of beauty in determining the
marriages of mankind--Attention paid by savages to ornaments--Their ideas
of beauty in women--The tendency to exaggerate each natural peculiarity.
CHAPTER XX.
Secondary Sexual Characters of Man--continued.
On the effects of the continued selection of women according to a different
standard of beauty in each race--On the causes which interfere with sexual
selection in civilised and savage nations--Conditions favourable to sexual
selection during primeval times--On the manner of action of sexual
selection with mankind--On the women in savage tribes having some power to
choose their husbands--Absence of hair on the body, and development of the
beard--Colour of the skin--Summary.
CHAPTER XXI.
General Summary and Conclusion.
Main conclusion that man is descended from some lower form--Manner of
development--Genealogy of man--Intellectual and moral faculties--Sexual
selection--Concluding remarks.
SUPPLEMENTAL NOTE.
INDEX.
THE DESCENT OF MAN; AND SELECTION IN RELATION TO SEX.
...
INTRODUCTION.
The nature of the following work will be best understood by a brief account
of how it came to be written. During many years I collected notes on the
origin or descent of man, without any intention of publishing on the
subject, but rather with the determination not to publish, as I thought
that I should thus only add to the prejudices against my views. It seemed
to me sufficient to indicate, in the first edition of my 'Origin of
Species,' that by this work "light would be thrown on the origin of man and
his history;" and this implies that man must be included with other organic
beings in any general conclusion respecting his manner of appearance on
this earth. Now the case wears a wholly different aspect. When a
naturalist like Carl Vogt ventures to say in his address as President of
the National Institution of Geneva (1869), "personne, en Europe au moins,
n'ose plus soutenir la creation independante et de toutes pieces, des
especes," it is manifest that at least a large number of naturalists must
admit that species are the modified descendants of other species; and this
especially holds good with the younger and rising naturalists. The greater
number accept the agency of natural selection; though some urge, whether
with justice the future must decide, that I have greatly overrated its
importance. Of the older and honoured chiefs in natural science, many
unfortunately are still opposed to evolution in every form.
In consequence of the views now adopted by most naturalists, and which will
ultimately, as in every other case, be followed by others who are not
scientific, I have been led to put together my notes, so as to see how far
the general conclusions arrived at in my former works were applicable to
man. This seemed all the more desirable, as I had never deliberately
applied these views to a species taken singly. When we confine our
attention to any one form, we are deprived of the weighty arguments derived
from the nature of the affinities which connect together whole groups of
organisms--their geographical distribution in past and present times, and
their geological succession. The homological structure, embryological
development, and rudimentary organs of a species remain to be considered,
whether it be man or any other animal, to which our attention may be
directed; but these great classes of facts afford, as it appears to me,
ample and conclusive evidence in favour of the principle of gradual
evolution. The strong support derived from the other arguments should,
however, always be kept before the mind.
The sole object of this work is to consider, firstly, whether man, like
every other species, is descended from some pre-existing form; secondly,
the manner of his development; and thirdly, the value of the differences
between the so-called races of man. As I shall confine myself to these
points, it will not be necessary to describe in detail the differences
between the several races--an enormous subject which has been fully
described in many valuable works. The high antiquity of man has recently
been demonstrated by the labours of a host of eminent men, beginning with
M. Boucher de Perthes; and this is the indispensable basis for
understanding his origin. I shall, therefore, take this conclusion for
granted, and may refer my readers to the admirable treatises of Sir Charles
Lyell, Sir John Lubbock, and others. Nor shall I have occasion to do more
than to allude to the amount of difference between man and the
anthropomorphous apes; for Prof. Huxley, in the opinion of most competent
judges, has conclusively shewn that in every visible character man differs
less from the higher apes, than these do from the lower members of the same
order of Primates.
This work contains hardly any original facts in regard to man; but as the
conclusions at which I arrived, after drawing up a rough draft, appeared to
me interesting, I thought that they might interest others. It has often
and confidently been asserted, that man's origin can never be known: but
ignorance more frequently begets confidence than does knowledge: it is
those who know little, and not those who know much, who so positively
assert that this or that problem will never be solved by science. The
conclusion that man is the co-descendant with other species of some
ancient, lower, and extinct form, is not in any degree new. Lamarck long
ago came to this conclusion, which has lately been maintained by several
eminent naturalists and philosophers; for instance, by Wallace, Huxley,
Lyell, Vogt, Lubbock, Buchner, Rolle, etc. (1. As the works of the first-
named authors are so well known, I need not give the titles; but as those
of the latter are less well known in England, I will give them:--'Sechs
Vorlesungen uber die Darwin'sche Theorie:' zweite Auflage, 1868, von Dr L.
Buchner; translated into French under the title 'Conferences sur la Theorie
Darwinienne,' 1869. 'Der Mensch im Lichte der Darwin'sche Lehre,' 1865,
von Dr. F. Rolle. I will not attempt to give references to all the authors
who have taken the same side of the question. Thus G. Canestrini has
published ('Annuario della Soc. d. Nat.,' Modena, 1867, page 81) a very
curious paper on rudimentary characters, as bearing on the origin of man.
Another work has (1869) been published by Dr. Francesco Barrago, bearing in
Italian the title of "Man, made in the image of God, was also made in the
image of the ape."), and especially by Haeckel. This last naturalist,
besides his great work, 'Generelle Morphologie' (1866), has recently (1868,
with a second edition in 1870), published his 'Naturliche
Schopfungsgeschichte,' in which he fully discusses the genealogy of man.
If this work had appeared before my essay had been written, I should
probably never have completed it. Almost all the conclusions at which I
have arrived I find confirmed by this naturalist, whose knowledge on many
points is much fuller than mine. Wherever I have added any fact or view
from Prof. Haeckel's writings, I give his authority in the text; other
statements I leave as they originally stood in my manuscript, occasionally
giving in the foot-notes references to his works, as a confirmation of the
more doubtful or interesting points.
During many years it has seemed to me highly probable that sexual selection
has played an important part in differentiating the races of man; but in my
'Origin of Species' (first edition, page 199) I contented myself by merely
alluding to this belief. When I came to apply this view to man, I found it
indispensable to treat the whole subject in full detail. (2. Prof.
Haeckel was the only author who, at the time when this work first appeared,
had discussed the subject of sexual selection, and had seen its full
importance, since the publication of the 'Origin'; and this he did in a
very able manner in his various works.) Consequently the second part of
the present work, treating of sexual selection, has extended to an
inordinate length, compared with the first part; but this could not be
avoided.
I had intended adding to the present volumes an essay on the expression of
the various emotions by man and the lower animals. My attention was called
to this subject many years ago by Sir Charles Bell's admirable work. This
illustrious anatomist maintains that man is endowed with certain muscles
solely for the sake of expressing his emotions. As this view is obviously
opposed to the belief that man is descended from some other and lower form,
it was necessary for me to consider it. I likewise wished to ascertain how
far the emotions are expressed in the same manner by the different races of
man. But owing to the length of the present work, I have thought it better
to reserve my essay for separate publication.
PART I. THE DESCENT OR ORIGIN OF MAN.
CHAPTER I.
THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM.
Nature of the evidence bearing on the origin of man--Homologous structures
in man and the lower animals--Miscellaneous points of correspondence--
Development--Rudimentary structures, muscles, sense-organs, hair, bones,
reproductive organs, etc.--The bearing of these three great classes of
facts on the origin of man.
He who wishes to decide whether man is the modified descendant of some pre-
existing form, would probably first enquire whether man varies, however
slightly, in bodily structure and in mental faculties; and if so, whether
the variations are transmitted to his offspring in accordance with the laws
which prevail with the lower animals. Again, are the variations the
result, as far as our ignorance permits us to judge, of the same general
causes, and are they governed by the same general laws, as in the case of
other organisms; for instance, by correlation, the inherited effects of use
and disuse, etc.? Is man subject to similar malconformations, the result
of arrested development, of reduplication of parts, etc., and does he
display in any of his anomalies reversion to some former and ancient type
of structure? It might also naturally be enquired whether man, like so
many other animals, has given rise to varieties and sub-races, differing
but slightly from each other, or to races differing so much that they must
be classed as doubtful species? How are such races distributed over the
world; and how, when crossed, do they react on each other in the first and
succeeding generations? And so with many other points.
The enquirer would next come to the important point, whether man tends to
increase at so rapid a rate, as to lead to occasional severe struggles for
existence; and consequently to beneficial variations, whether in body or
mind, being preserved, and injurious ones eliminated. Do the races or
species of men, whichever term may be applied, encroach on and replace one
another, so that some finally become extinct? We shall see that all these
questions, as indeed is obvious in respect to most of them, must be
answered in the affirmative, in the same manner as with the lower animals.
But the several considerations just referred to may be conveniently
deferred for a time: and we will first see how far the bodily structure of
man shews traces, more or less plain, of his descent from some lower form.
In succeeding chapters the mental powers of man, in comparison with those
of the lower animals, will be considered.
THE BODILY STRUCTURE OF MAN.
It is notorious that man is constructed on the same general type or model
as other mammals. All the bones in his skeleton can be compared with
corresponding bones in a monkey, bat, or seal. So it is with his muscles,
nerves, blood-vessels and internal viscera. The brain, the most important
of all the organs, follows the same law, as shewn by Huxley and other
anatomists. Bischoff (1. 'Grosshirnwindungen des Menschen,' 1868, s. 96.
The conclusions of this author, as well as those of Gratiolet and Aeby,
concerning the brain, will be discussed by Prof. Huxley in the Appendix
alluded to in the Preface to this edition.), who is a hostile witness,
admits that every chief fissure and fold in the brain of man has its
analogy in that of the orang; but he adds that at no period of development
do their brains perfectly agree; nor could perfect agreement be expected,
for otherwise their mental powers would have been the same. Vulpian (2.
'Lec. sur la Phys.' 1866, page 890, as quoted by M. Dally, 'L'Ordre des
Primates et le Transformisme,' 1868, page 29.), remarks: "Les differences
reelles qui existent entre l'encephale de l'homme et celui des singes
superieurs, sont bien minimes. Il ne faut pas se faire d'illusions a cet
egard. L'homme est bien plus pres des singes anthropomorphes par les
caracteres anatomiques de son cerveau que ceux-ci ne le sont non seulement
des autres mammiferes, mais meme de certains quadrumanes, des guenons et
des macaques." But it would be superfluous here to give further details on
the correspondence between man and the higher mammals in the structure of
the brain and all other parts of the body.
It may, however, be worth while to specify a few points, not directly or
obviously connected with structure, by which this correspondence or
relationship is well shewn.
Man is liable to receive from the lower animals, and to communicate to
them, certain diseases, as hydrophobia, variola, the glanders, syphilis,
cholera, herpes, etc. (3. Dr. W. Lauder Lindsay has treated this subject
at some length in the 'Journal of Mental Science,' July 1871; and in the
'Edinburgh Veterinary Review,' July 1858.); and this fact proves the close
similarity (4. A Reviewer has criticised ('British Quarterly Review,' Oct.
1st, 1871, page 472) what I have here said with much severity and contempt;
but as I do not use the term identity, I cannot see that I am greatly in
error. There appears to me a strong analogy between the same infection or
contagion producing the same result, or one closely similar, in two
distinct animals, and the testing of two distinct fluids by the same
chemical reagent.) of their tissues and blood, both in minute structure and
composition, far more plainly than does their comparison under the best
microscope, or by the aid of the best chemical analysis. Monkeys are
liable to many of the same non-contagious diseases as we are; thus Rengger
(5. 'Naturgeschichte der Saugethiere von Paraguay,' 1830, s. 50.), who
carefully observed for a long time the Cebus Azarae in its native land,
found it liable to catarrh, with the usual symptoms, and which, when often
recurrent, led to consumption. These monkeys suffered also from apoplexy,
inflammation of the bowels, and cataract in the eye. The younger ones when
shedding their milk-teeth often died from fever. Medicines produced the
same effect on them as on us. Many kinds of monkeys have a strong taste
for tea, coffee, and spiritous liquors: they will also, as I have myself
seen, smoke tobacco with pleasure. (6. The same tastes are common to some
animals much lower in the scale. Mr. A. Nichols informs me that he kept in
Queensland, in Australia, three individuals of the Phaseolarctus cinereus;
and that, without having been taught in any way, they acquired a strong
taste for rum, and for smoking tobacco.) Brehm asserts that the natives of
north-eastern Africa catch the wild baboons by exposing vessels with strong
beer, by which they are made drunk. He has seen some of these animals,
which he kept in confinement, in this state; and he gives a laughable
account of their behaviour and strange grimaces. On the following morning
they were very cross and dismal; they held their aching heads with both
hands, and wore a most pitiable expression: when beer or wine was offered
them, they turned away with disgust, but relished the juice of lemons. (7.
Brehm, 'Thierleben,' B. i. 1864, s. 75, 86. On the Ateles, s. 105. For
other analogous statements, see s. 25, 107.) An American monkey, an
Ateles, after getting drunk on brandy, would never touch it again, and thus
was wiser than many men. These trifling facts prove how similar the nerves
of taste must be in monkeys and man, and how similarly their whole nervous
system is affected.
Man is infested with internal parasites, sometimes causing fatal effects;
and is plagued by external parasites, all of which belong to the same
genera or families as those infesting other mammals, and in the case of
scabies to the same species. (8. Dr. W. Lauder Lindsay, 'Edinburgh Vet.
Review,' July 1858, page 13.) Man is subject, like other mammals, birds,
and even insects (9. With respect to insects see Dr. Laycock, "On a
General Law of Vital Periodicity," 'British Association,' 1842. Dr.
Macculloch, 'Silliman's North American Journal of Science,' vol. XVII. page
305, has seen a dog suffering from tertian ague. Hereafter I shall return
to this subject.), to that mysterious law, which causes certain normal
processes, such as gestation, as well as the maturation and duration of
various diseases, to follow lunar periods. His wounds are repaired by the
same process of healing; and the stumps left after the amputation of his
limbs, especially during an early embryonic period, occasionally possess
some power of regeneration, as in the lowest animals. (10. I have given
the evidence on this head in my 'Variation of Animals and Plants under
Domestication,' vol. ii. page 15, and more could be added.)
The whole process of that most important function, the reproduction of the
species, is strikingly the same in all mammals, from the first act of
courtship by the male (11. Mares e diversis generibus Quadrumanorum sine
dubio dignoscunt feminas humanas a maribus. Primum, credo, odoratu, postea
aspectu. Mr. Youatt, qui diu in Hortis Zoologicis (Bestiariis) medicus
animalium erat, vir in rebus observandis cautus et sagax, hoc mihi
certissime probavit, et curatores ejusdem loci et alii e ministris
confirmaverunt. Sir Andrew Smith et Brehm notabant idem in Cynocephalo.
Illustrissimus Cuvier etiam narrat multa de hac re, qua ut opinor, nihil
turpius potest indicari inter omnia hominibus et Quadrumanis communia.
Narrat enim Cynocephalum quendam in furorem incidere aspectu feminarum
aliquarem, sed nequaquam accendi tanto furore ab omnibus. Semper eligebat
juniores, et dignoscebat in turba, et advocabat voce gestuque.), to the
birth and nurturing of the young. Monkeys are born in almost as helpless a
condition as our own infants; and in certain genera the young differ fully
as much in appearance from the adults, as do our children from their
full-grown parents. (12. This remark is made with respect to Cynocephalus
and the anthropomorphous apes by Geoffroy Saint-Hilaire and F. Cuvier,
'Histoire Nat. des Mammiferes,' tom. i. 1824.) It has been urged by some
writers, as an important distinction, that with man the young arrive at
maturity at a much later age than with any other animal: but if we look to
the races of mankind which inhabit tropical countries the difference is not
great, for the orang is believed not to be adult till the age of from ten
to fifteen years. (13. Huxley, 'Man's Place in Nature,' 1863, p. 34.)
Man differs from woman in size, bodily strength, hairiness, etc., as well
as in mind, in the same manner as do the two sexes of many mammals. So
that the correspondence in general structure, in the minute structure of
the tissues, in chemical composition and in constitution, between man and
the higher animals, especially the anthropomorphous apes, is extremely
close.
EMBRYONIC DEVELOPMENT.
[Fig. 1. Shows a human embryo, from Ecker, and a dog embryo, from
Bischoff. Labelled in each are:
a. Fore-brain, cerebral hemispheres, etc.
b. Mid-brain, corpora quadrigemina.
c. Hind-brain, cerebellum, medulla oblongata.
d. Eye.
e. Ear.
f. First visceral arch.
g. Second visceral arch.
H. Vertebral columns and muscles in process of development.
i. Anterior extremities.
K. Posterior extremities.
L. Tail or os coccyx.]
Man is developed from an ovule, about the 125th of an inch in diameter,
which differs in no respect from the ovules of other animals. The embryo
itself at a very early period can hardly be distinguished from that of
other members of the vertebrate kingdom. At this period the arteries run
in arch-like branches, as if to carry the blood to branchiae which are not
present in the higher Vertebrata, though the slits on the sides of the neck
still remain (see f, g, fig. 1), marking their former position. At a
somewhat later period, when the extremities are developed, "the feet of
lizards and mammals," as the illustrious Von Baer remarks, "the wings and
feet of birds, no less than the hands and feet of man, all arise from the
same fundamental form." It is, says Prof. Huxley (14. 'Man's Place in
Nature,' 1863, p. 67.), "quite in the later stages of development that the
young human being presents marked differences from the young ape, while the
latter departs as much from the dog in its developments, as the man does.
Startling as this last assertion may appear to be, it is demonstrably
true."
As some of my readers may never have seen a drawing of an embryo, I have
given one of man and another of a dog, at about the same early stage of
development, carefully copied from two works of undoubted accuracy. (15.
The human embryo (upper fig.) is from Ecker, 'Icones Phys.,' 1851-1859,
tab. xxx. fig. 2. This embryo was ten lines in length, so that the drawing
is much magnified. The embryo of the dog is from Bischoff,
'Entwicklungsgeschichte des Hunde-Eies,' 1845, tab. xi. fig. 42B. This
drawing is five times magnified, the embryo being twenty-five days old.
The internal viscera have been omitted, and the uterine appendages in both
drawings removed. I was directed to these figures by Prof. Huxley, from
whose work, 'Man's Place in Nature,' the idea of giving them was taken.
Haeckel has also given analogous drawings in his 'Schopfungsgeschichte.')
After the foregoing statements made by such high authorities, it would be
superfluous on my part to give a number of borrowed details, shewing that
the embryo of man closely resembles that of other mammals. It may,
however, be added, that the human embryo likewise resembles certain low
forms when adult in various points of structure. For instance, the heart
at first exists as a simple pulsating vessel; the excreta are voided
through a cloacal passage; and the os coccyx projects like a true tail,
"extending considerably beyond the rudimentary legs." (16. Prof. Wyman in
'Proceedings of the American Academy of Sciences,' vol. iv. 1860, p. 17.)
In the embryos of all air-breathing vertebrates, certain glands, called the
corpora Wolffiana, correspond with, and act like the kidneys of mature
fishes. (17. Owen, 'Anatomy of Vertebrates,' vol. i. p. 533.) Even at a
later embryonic period, some striking resemblances between man and the
lower animals may be observed. Bischoff says that "the convolutions of the
brain in a human foetus at the end of the seventh month reach about the
same stage of development as in a baboon when adult." (18. 'Die
Grosshirnwindungen des Menschen,' 1868, s. 95.) The great toe, as
Professor Owen remarks (19. 'Anatomy of Vertebrates,' vol. ii. p. 553.),
"which forms the fulcrum when standing or walking, is perhaps the most
characteristic peculiarity in the human structure;" but in an embryo, about
an inch in length, Prof. Wyman (20. 'Proc. Soc. Nat. Hist.' Boston, 1863,
vol. ix. p. 185.) found "that the great toe was shorter than the others;
and, instead of being parallel to them, projected at an angle from the side
of the foot, thus corresponding with the permanent condition of this part
in the quadrumana." I will conclude with a quotation from Huxley (21.
'Man's Place in Nature,' p. 65.) who after asking, does man originate in a
different way from a dog, bird, frog or fish? says, "the reply is not
doubtful for a moment; without question, the mode of origin, and the early
stages of the development of man, are identical with those of the animals
immediately below him in the scale: without a doubt in these respects, he
is far nearer to apes than the apes are to the dog."
RUDIMENTS.
This subject, though not intrinsically more important than the two last,
will for several reasons be treated here more fully. (22. I had written a
rough copy of this chapter before reading a valuable paper, "Caratteri
rudimentali in ordine all' origine dell' uomo" ('Annuario della Soc. d.
Naturalisti,' Modena, 1867, p. 81), by G. Canestrini, to which paper I am
considerably indebted. Haeckel has given admirable discussions on this
whole subject, under the title of Dysteleology, in his 'Generelle
Morphologie' and 'Schopfungsgeschichte.') Not one of the higher animals
can be named which does not bear some part in a rudimentary condition; and
man forms no exception to the rule. Rudimentary organs must be
distinguished from those that are nascent; though in some cases the
distinction is not easy. The former are either absolutely useless, such as
the mammae of male quadrupeds, or the incisor teeth of ruminants which
never cut through the gums; or they are of such slight service to their
present possessors, that we can hardly suppose that they were developed
under the conditions which now exist. Organs in this latter state are not
strictly rudimentary, but they are tending in this direction. Nascent
organs, on the other hand, though not fully developed, are of high service
to their possessors, and are capable of further development. Rudimentary
organs are eminently variable; and this is partly intelligible, as they are
useless, or nearly useless, and consequently are no longer subjected to
natural selection. They often become wholly suppressed. When this occurs,
they are nevertheless liable to occasional reappearance through reversion--
a circumstance well worthy of attention.
The chief agents in causing organs to become rudimentary seem to have been
disuse at that period of life when the organ is chiefly used (and this is
generally during maturity), and also inheritance at a corresponding period
of life. The term "disuse" does not relate merely to the lessened action
of muscles, but includes a diminished flow of blood to a part or organ,
from being subjected to fewer alternations of pressure, or from becoming in
any way less habitually active. Rudiments, however, may occur in one sex
of those parts which are normally present in the other sex; and such
rudiments, as we shall hereafter see, have often originated in a way
distinct from those here referred to. In some cases, organs have been
reduced by means of natural selection, from having become injurious to the
species under changed habits of life. The process of reduction is probably
often aided through the two principles of compensation and economy of
growth; but the later stages of reduction, after disuse has done all that
can fairly be attributed to it, and when the saving to be effected by the
economy of growth would be very small (23. Some good criticisms on this
subject have been given by Messrs. Murie and Mivart, in 'Transact.
Zoological Society,' 1869, vol. vii. p. 92.), are difficult to understand.
The final and complete suppression of a part, already useless and much
reduced in size, in which case neither compensation nor economy can come
into play, is perhaps intelligible by the aid of the hypothesis of
pangenesis. But as the whole subject of rudimentary organs has been
discussed and illustrated in my former works (24. 'Variation of Animals
and Plants under Domestication,' vol. ii pp. 317 and 397. See also 'Origin
of Species,' 5th Edition p. 535.), I need here say no more on this head.
Rudiments of various muscles have been observed in many parts of the human
body (25. For instance, M. Richard ('Annales des Sciences Nat.,' 3rd
series, Zoolog. 1852, tom. xviii. p. 13) describes and figures rudiments of
what he calls the "muscle pedieux de la main," which he says is sometimes
"infiniment petit." Another muscle, called "le tibial posterieur," is
generally quite absent in the hand, but appears from time to time in a more
or less rudimentary condition.); and not a few muscles, which are regularly
present in some of the lower animals can occasionally be detected in man in
a greatly reduced condition. Every one must have noticed the power which
many animals, especially horses, possess of moving or twitching their skin;
and this is effected by the panniculus carnosus. Remnants of this muscle
in an efficient state are found in various parts of our bodies; for
instance, the muscle on the forehead, by which the eyebrows are raised.
The platysma myoides, which is well developed on the neck, belongs to this
system. Prof. Turner, of Edinburgh, has occasionally detected, as he
informs me, muscular fasciculi in five different situations, namely in the
axillae, near the scapulae, etc., all of which must be referred to the
system of the panniculus. He has also shewn (26. Prof. W. Turner,
'Proceedings of the Royal Society of Edinburgh,' 1866-67, p. 65.) that the
musculus sternalis or sternalis brutorum, which is not an extension of the
rectus abdominalis, but is closely allied to the panniculus, occurred in
the proportion of about three per cent. in upwards of 600 bodies: he adds,
that this muscle affords "an excellent illustration of the statement that
occasional and rudimentary structures are especially liable to variation in
arrangement."
Some few persons have the power of contracting the superficial muscles on
their scalps; and these muscles are in a variable and partially rudimentary
condition. M. A. de Candolle has communicated to me a curious instance of
the long-continued persistence or inheritance of this power, as well as of
its unusual development. He knows a family, in which one member, the
present head of the family, could, when a youth, pitch several heavy books
from his head by the movement of the scalp alone; and he won wagers by
performing this feat. His father, uncle, grandfather, and his three
children possess the same power to the same unusual degree. This family
became divided eight generations ago into two branches; so that the head of
the above-mentioned branch is cousin in the seventh degree to the head of
the other branch. This distant cousin resides in another part of France;
and on being asked whether he possessed the same faculty, immediately
exhibited his power. This case offers a good illustration how persistent
may be the transmission of an absolutely useless faculty, probably derived
from our remote semi-human progenitors; since many monkeys have, and
frequently use the power, of largely moving their scalps up and down. (27.
See my 'Expression of the Emotions in Man and Animals,' 1872, p. 144.)
The extrinsic muscles which serve to move the external ear, and the
intrinsic muscles which move the different parts, are in a rudimentary
condition in man, and they all belong to the system of the panniculus; they
are also variable in development, or at least in function. I have seen one
man who could draw the whole ear forwards; other men can draw it upwards;
another who could draw it backwards (28. Canestrini quotes Hyrtl.
('Annuario della Soc. dei Naturalisti,' Modena, 1867, p. 97) to the same
effect.); and from what one of these persons told me, it is probable that
most of us, by often touching our ears, and thus directing our attention
towards them, could recover some power of movement by repeated trials. The
power of erecting and directing the shell of the ears to the various points
of the compass, is no doubt of the highest service to many animals, as they
thus perceive the direction of danger; but I have never heard, on
sufficient evidence, of a man who possessed this power, the one which might
be of use to him. The whole external shell may be considered a rudiment,
together with the various folds and prominences (helix and anti-helix,
tragus and anti-tragus, etc.) which in the lower animals strengthen and
support the ear when erect, without adding much to its weight. Some
authors, however, suppose that the cartilage of the shell serves to
transmit vibrations to the acoustic nerve; but Mr. Toynbee (29. 'The
Diseases of the Ear,' by J. Toynbee, F.R.S., 1860, p. 12. A distinguished
physiologist, Prof. Preyer, informs me that he had lately been
experimenting on the function of the shell of the ear, and has come to
nearly the same conclusion as that given here.), after collecting all the
known evidence on this head, concludes that the external shell is of no
distinct use. The ears of the chimpanzee and orang are curiously like
those of man, and the proper muscles are likewise but very slightly
developed. (30. Prof. A. Macalister, 'Annals and Magazine of Natural
History,' vol. vii. 1871, p. 342.) I am also assured by the keepers in the
Zoological Gardens that these animals never move or erect their ears; so
that they are in an equally rudimentary condition with those of man, as far
as function is concerned. Why these animals, as well as the progenitors of
man, should have lost the power of erecting their ears, we cannot say. It
may be, though I am not satisfied with this view, that owing to their
arboreal habits and great strength they were but little exposed to danger,
and so during a lengthened period moved their ears but little, and thus
gradually lost the power of moving them. This would be a parallel case
with that of those large and heavy birds, which, from ihabiting oceanic
islands, have not been exposed to the attacks of beasts of prey, and have
consequently lost the power of using their wings for flight. The inability
to move the ears in man and several apes is, however, partly compensated by
the freedom with which they can move the head in a horizontal plane, so as
to catch sounds from all directions. It has been asserted that the ear of
man alone possesses a lobule; but "a rudiment of it is found in the
gorilla" (31. Mr. St. George Mivart, 'Elementary Anatomy,' 1873, p. 396.);
and, as I hear from Prof. Preyer, it is not rarely absent in the negro.
[Fig. 2. Human Ear, modelled and drawn by Mr. Woolner. The projecting
point is labelled a.]
The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity
in the external ear, which he has often observed both in men and women, and
of which he perceived the full significance. His attention was first
called to the subject whilst at work on his figure of Puck, to which he had
given pointed ears. He was thus led to examine the ears of various
monkeys, and subsequently more carefully those of man. The peculiarity
consists in a little blunt point, projecting from the inwardly folded
margin, or helix. When present, it is developed at birth, and, according
to Prof. Ludwig Meyer, more frequently in man than in woman. Mr. Woolner
made an exact model of one such case, and sent me the accompanying drawing.
(Fig. 2). These points not only project inwards towards the centre of the
ear, but often a little outwards from its plane, so as to be visible when
the head is viewed from directly in front or behind. They are variable in
size, and somewhat in position, standing either a little higher or lower;
and they sometimes occur on one ear and not on the other. They are not
confined to mankind, for I observed a case in one of the spider-monkeys
(Ateles beelzebuth) in our Zoological Gardens; and Mr. E. Ray Lankester
informs me of another case in a chimpanzee in the gardens at Hamburg. The
helix obviously consists of the extreme margin of the ear folded inwards;
and this folding appears to be in some manner connected with the whole
external ear being permanently pressed backwards. In many monkeys, which
do not stand high in the order, as baboons and some species of macacus (32.
See also some remarks, and the drawings of the ears of the Lemuroidea, in
Messrs. Murie and Mivart's excellent paper in 'Transactions of the
Zoological Society,' vol. vii. 1869, pp. 6 and 90.), the upper portion of
the ear is slightly pointed, and the margin is not at all folded inwards;
but if the margin were to be thus folded, a slight point would necessarily
project inwards towards the centre, and probably a little outwards from the
plane of the ear; and this I believe to be their origin in many cases. On
the other hand, Prof. L. Meyer, in an able paper recently published (33.
'Uber das Darwin'sche Spitzohr,' Archiv fur Path. Anat. und Phys., 1871, p.
485.), maintains that the whole case is one of mere variability; and that
the projections are not real ones, but are due to the internal cartilage on
each side of the points not having been fully developed. I am quite ready
to admit that this is the correct explanation in many instances, as in
those figured by Prof. Meyer, in which there are several minute points, or
the whole margin is sinuous. I have myself seen, through the kindness of
Dr. L. Down, the ear of a microcephalous idiot, on which there is a
projection on the outside of the helix, and not on the inward folded edge,
so that this point can have no relation to a former apex of the ear.
Nevertheless in some cases, my original view, that the points are vestiges
of the tips of formerly erect and pointed ears, still seems to me probable.
I think so from the frequency of their occurrence, and from the general
correspondence in position with that of the tip of a pointed ear. In one
case, of which a photograph has been sent me, the projection is so large,
that supposing, in accordance with Prof. Meyer's view, the ear to be made
perfect by the equal development of the cartilage throughout the whole
extent of the margin, it would have covered fully one-third of the whole
ear. Two cases have been communicated to me, one in North America, and the
other in England, in which the upper margin is not at all folded inwards,
but is pointed, so that it closely resembles the pointed ear of an ordinary
quadruped in outline. In one of these cases, which was that of a young
child, the father compared the ear with the drawing which I have given (34.
'The Expression of the Emotions,' p. 136.) of the ear of a monkey, the
Cynopithecus niger, and says that their outlines are closely similar. If,
in these two cases, the margin had been folded inwards in the normal
manner, an inward projection must have been formed. I may add that in two
other cases the outline still remains somewhat pointed, although the margin
of the upper part of the ear is normally folded inwards--in one of them,
however, very narrowly. [Fig.3. Foetus of an Orang(?). Exact copy of a
photograph, shewing the form of the ear at this early age.] The following
woodcut (No. 3) is an accurate copy of a photograph of the foetus of an
orang (kindly sent me by Dr. Nitsche), in which it may be seen how
different the pointed outline of the ear is at this period from its adult
condition, when it bears a close general resemblance to that of man. It is
evident that the folding over of the tip of such an ear, unless it changed
greatly during its further development, would give rise to a point
projecting inwards. On the whole, it still seems to me probable that the
points in question are in some cases, both in man and apes, vestiges of a
former condition.
The nictitating membrane, or third eyelid, with its accessory muscles and
other structures, is especially well developed in birds, and is of much
functional importance to them, as it can be rapidly drawn across the whole
eye-ball. It is found in some reptiles and amphibians, and in certain
fishes, as in sharks. It is fairly well developed in the two lower
divisions of the mammalian series, namely, in the monotremata and
marsupials, and in some few of the higher mammals, as in the walrus. But
in man, the quadrumana, and most other mammals, it exists, as is admitted
by all anatomists, as a mere rudiment, called the semilunar fold. (35.
Muller's 'Elements of Physiology,' Eng. translat. 1842, vol. ii. p. 1117.
Owen, 'Anatomy of Vertebrates,' vol. iii. p. 260; ibid. on the Walrus,
'Proceedings of the Zoological Society,' November 8, 1854. See also R.
Knox, 'Great Artists and Anatomists,' p. 106. This rudiment apparently is
somewhat larger in Negroes and Australians than in Europeans, see Carl
Vogt, 'Lectures on Man,' Eng. translat. p. 129.)
The sense of smell is of the highest importance to the greater number of
mammals--to some, as the ruminants, in warning them of danger; to others,
as the Carnivora, in finding their prey; to others, again, as the wild
boar, for both purposes combined. But the sense of smell is of extremely
slight service, if any, even to the dark coloured races of men, in whom it
is much more highly developed than in the white and civilised races. (36.
The account given by Humboldt of the power of smell possessed by the
natives of South America is well known, and has been confirmed by others.
M. Houzeau ('Etudes sur les Facultes Mentales,' etc., tom. i. 1872, p. 91)
asserts that he repeatedly made experiments, and proved that Negroes and
Indians could recognise persons in the dark by their odour. Dr. W. Ogle
has made some curious observations on the connection between the power of
smell and the colouring matter of the mucous membrane of the olfactory
region as well as of the skin of the body. I have, therefore, spoken in
the text of the dark-coloured races having a finer sense of smell than the
white races. See his paper, 'Medico-Chirurgical Transactions,' London,
vol. liii. 1870, p. 276.) Nevertheless it does not warn them of danger,
nor guide them to their food; nor does it prevent the Esquimaux from
sleeping in the most fetid atmosphere, nor many savages from eating
half-putrid meat. In Europeans the power differs greatly in different
individuals, as I am assured by an eminent naturalist who possesses this
sense highly developed, and who has attended to the subject. Those who
believe in the principle of gradual evolution, will not readily admit that
the sense of smell in its present state was originally acquired by man, as
he now exists. He inherits the power in an enfeebled and so far
rudimentary condition, from some early progenitor, to whom it was highly
serviceable, and by whom it was continually used. In those animals which
have this sense highly developed, such as dogs and horses, the recollection
of persons and of places is strongly associated with their odour; and we
can thus perhaps understand how it is, as Dr. Maudsley has truly remarked
(37. 'The Physiology and Pathology of Mind,' 2nd ed. 1868, p. 134.), that
the sense of smell in man "is singularly effective in recalling vividly the
ideas and images of forgotten scenes and places."
Man differs conspicuously from all the other primates in being almost
naked. But a few short straggling hairs are found over the greater part of
the body in the man, and fine down on that of the woman. The different
races differ much in hairiness; and in the individuals of the same race the
hairs are highly variable, not only in abundance, but likewise in position:
thus in some Europeans the shoulders are quite naked, whilst in others they
bear thick tufts of hair. (38. Eschricht, Uber die Richtung der Haare am
menschlichen Korper, Muller's 'Archiv fur Anat. und Phys.' 1837, s. 47. I
shall often have to refer to this very curious paper.) There can be little
doubt that the hairs thus scattered over the body are the rudiments of the
uniform hairy coat of the lower animals. This view is rendered all the
more probable, as it is known that fine, short, and pale-coloured hairs on
the limbs and other parts of the body, occasionally become developed into
"thickset, long, and rather coarse dark hairs," when abnormally nourished
near old-standing inflamed surfaces. (39. Paget, 'Lectures on Surgical
Pathology,' 1853, vol. i. p. 71.)
I am informed by Sir James Paget that often several members of a family
have a few hairs in their eyebrows much longer than the others; so that
even this slight peculiarity seems to be inherited. These hairs, too, seem
to have their representatives; for in the chimpanzee, and in certain
species of Macacus, there are scattered hairs of considerable length rising
from the naked skin above the eyes, and corresponding to our eyebrows;
similar long hairs project from the hairy covering of the superciliary
ridges in some baboons.
The fine wool-like hair, or so-called lanugo, with which the human foetus
during the sixth month is thickly covered, offers a more curious case. It
is first developed, during the fifth month, on the eyebrows and face, and
especially round the mouth, where it is much longer than that on the head.
A moustache of this kind was observed by Eschricht (40. Eschricht, ibid.
s. 40, 47.) on a female foetus; but this is not so surprising a
circumstance as it may at first appear, for the two sexes generally
resemble each other in all external characters during an early period of
growth. The direction and arrangement of the hairs on all parts of the
foetal body are the same as in the adult, but are subject to much
variability. The whole surface, including even the forehead and ears, is
thus thickly clothed; but it is a significant fact that the palms of the
hands and the soles of the feet are quite naked, like the inferior surfaces
of all four extremities in most of the lower animals. As this can hardly
be an accidental coincidence, the woolly covering of the foetus probably
represents the first permanent coat of hair in those mammals which are born
hairy. Three or four cases have been recorded of persons born with their
whole bodies and faces thickly covered with fine long hairs; and this
strange condition is strongly inherited, and is correlated with an abnormal
condition of the teeth. (41. See my 'Variation of Animals and Plants
under Domestication,' vol. ii. p. 327. Prof. Alex. Brandt has recently
sent me an additional case of a father and son, born in Russia, with these
peculiarities. I have received drawings of both from Paris.) Prof. Alex.
Brandt informs me that he has compared the hair from the face of a man thus
characterised, aged thirty-five, with the lanugo of a foetus, and finds it
quite similar in texture; therefore, as he remarks, the case may be
attributed to an arrest of development in the hair, together with its
continued growth. Many delicate children, as I have been assured by a
surgeon to a hospital for children, have their backs covered by rather long
silky hairs; and such cases probably come under the same head.
It appears as if the posterior molar or wisdom-teeth were tending to become
rudimentary in the more civilised races of man. These teeth are rather
smaller than the other molars, as is likewise the case with the
corresponding teeth in the chimpanzee and orang; and they have only two
separate fangs. They do not cut through the gums till about the
seventeenth year, and I have been assured that they are much more liable to
decay, and are earlier lost than the other teeth; but this is denied by
some eminent dentists. They are also much more liable to vary, both in
structure and in the period of their development, than the other teeth.
(42. Dr. Webb, 'Teeth in Man and the Anthropoid Apes,' as quoted by Dr. C.
Carter Blake in Anthropological Review, July 1867, p. 299.) In the
Melanian races, on the other hand, the wisdom-teeth are usually furnished
with three separate fangs, and are generally sound; they also differ from
the other molars in size, less than in the Caucasian races. (43. Owen,
'Anatomy of Vertebrates,' vol. iii. pp. 320, 321, and 325.) Prof.
Schaaffhausen accounts for this difference between the races by "the
posterior dental portion of the jaw being always shortened" in those that
are civilised (44. 'On the Primitive Form of the Skull,' Eng. translat.,
in 'Anthropological Review,' Oct. 1868, p. 426), and this shortening may, I
presume, be attributed to civilised men habitually feeding on soft, cooked
food, and thus using their jaws less. I am informed by Mr. Brace that it
is becoming quite a common practice in the United States to remove some of
the molar teeth of children, as the jaw does not grow large enough for the
perfect development of the normal number. (45. Prof. Montegazza writes to
me from Florence, that he has lately been studying the last molar teeth in
the different races of man, and has come to the same conclusion as that
given in my text, viz., that in the higher or civilised races they are on
the road towards atrophy or elimination.)
With respect to the alimentary canal, I have met with an account of only a
single rudiment, namely the vermiform appendage of the caecum. The caecum
is a branch or diverticulum of the intestine, ending in a cul-de-sac, and
is extremely long in many of the lower vegetable-feeding mammals. In the
marsupial koala it is actually more than thrice as long as the whole body.
(46. Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 416, 434, 441.) It is
sometimes produced into a long gradually-tapering point, and is sometimes
constricted in parts. It appears as if, in consequence of changed diet or
habits, the caecum had become much shortened in various animals, the
vermiform appendage being left as a rudiment of the shortened part. That
this appendage is a rudiment, we may infer from its small size, and from
the evidence which Prof. Canestrini (47. 'Annuario della Soc. d. Nat.'
Modena, 1867, p. 94.) has collected of its variability in man. It is
occasionally quite absent, or again is largely developed. The passage is
sometimes completely closed for half or two-thirds of its length, with the
terminal part consisting of a flattened solid expansion. In the orang this
appendage is long and convoluted: in man it arises from the end of the
short caecum, and is commonly from four to five inches in length, being
only about the third of an inch in diameter. Not only is it useless, but
it is sometimes the cause of death, of which fact I have lately heard two
instances: this is due to small hard bodies, such as seeds, entering the
passage, and causing inflammation. (48. M. C. Martins ("De l'Unite
Organique," in 'Revue des Deux Mondes,' June 15, 1862, p. 16) and Haeckel
('Generelle Morphologie,' B. ii. s. 278), have both remarked on the
singular fact of this rudiment sometimes causing death.)
In some of the lower Quadrumana, in the Lemuridae and Carnivora, as well as
in many marsupials, there is a passage near the lower end of the humerus,
called the supra-condyloid foramen, through which the great nerve of the
fore limb and often the great artery pass. Now in the humerus of man,
there is generally a trace of this passage, which is sometimes fairly well
developed, being formed by a depending hook-like process of bone, completed
by a band of ligament. Dr. Struthers (49. With respect to inheritance,
see Dr. Struthers in the 'Lancet,' Feb. 15, 1873, and another important
paper, ibid. Jan. 24, 1863, p. 83. Dr. Knox, as I am informed, was the
first anatomist who drew attention to this peculiar structure in man; see
his 'Great Artists and Anatomists,' p. 63. See also an important memoir on
this process by Dr. Gruber, in the 'Bulletin de l'Acad. Imp. de St.
Petersbourg,' tom. xii. 1867, p. 448.), who has closely attended to the
subject, has now shewn that this peculiarity is sometimes inherited, as it
has occurred in a father, and in no less than four out of his seven
children. When present, the great nerve invariably passes through it; and
this clearly indicates that it is the homologue and rudiment of the
supra-condyloid foramen of the lower animals. Prof. Turner estimates, as
he informs me, that it occurs in about one per cent. of recent skeletons.
But if the occasional development of this structure in man is, as seems
probable, due to reversion, it is a return to a very ancient state of
things, because in the higher Quadrumana it is absent.
There is another foramen or perforation in the humerus, occasionally
present in man, which may be called the inter-condyloid. This occurs, but
not constantly, in various anthropoid and other apes (50. Mr. St. George
Mivart, 'Transactions Phil. Soc.' 1867, p. 310.), and likewise in many of
the lower animals. It is remarkable that this perforation seems to have
been present in man much more frequently during ancient times than
recently. Mr. Busk (51. "On the Caves of Gibraltar," 'Transactions of the
International Congress of Prehistoric Archaeology,' Third Session, 1869, p.
159. Prof. Wyman has lately shewn (Fourth Annual Report, Peabody Museum,
1871, p. 20), that this perforation is present in thirty-one per cent. of
some human remains from ancient mounds in the Western United States, and in
Florida. It frequently occurs in the negro.) has collected the following
evidence on this head: Prof. Broca "noticed the perforation in four and a
half per cent. of the arm-bones collected in the 'Cimetiere du Sud,' at
Paris; and in the Grotto of Orrony, the contents of which are referred to
the Bronze period, as many as eight humeri out of thirty-two were
perforated; but this extraordinary proportion, he thinks, might be due to
the cavern having been a sort of 'family vault.' Again, M. Dupont found
thirty per cent. of perforated bones in the caves of the Valley of the
Lesse, belonging to the Reindeer period; whilst M. Leguay, in a sort of
dolmen at Argenteuil, observed twenty-five per cent. to be perforated; and
M. Pruner-Bey found twenty-six per cent. in the same condition in bones
from Vaureal. Nor should it be left unnoticed that M. Pruner-Bey states
that this condition is common in Guanche skeletons." It is an interesting
fact that ancient races, in this and several other cases, more frequently
present structures which resemble those of the lower animals than do the
modern. One chief cause seems to be that the ancient races stand somewhat
nearer in the long line of descent to their remote animal-like progenitors.
In man, the os coccyx, together with certain other vertebrae hereafter to
be described, though functionless as a tail, plainly represent this part in
other vertebrate animals. At an early embryonic period it is free, and
projects beyond the lower extremities; as may be seen in the drawing (Fig.
1.) of a human embryo. Even after birth it has been known, in certain rare
and anomalous cases (52. Quatrefages has lately collected the evidence on
this subject. 'Revue des Cours Scientifiques,' 1867-1868, p. 625. In 1840
Fleischmann exhibited a human foetus bearing a free tail, which, as is not
always the case, included vertebral bodies; and this tail was critically
examined by the many anatomists present at the meeting of naturalists at
Erlangen (see Marshall in Niederlandischen Archiv fur Zoologie, December
1871).), to form a small external rudiment of a tail. The os coccyx is
short, usually including only four vertebrae, all anchylosed together: and
these are in a rudimentary condition, for they consist, with the exception
of the basal one, of the centrum alone. (53. Owen, 'On the Nature of
Limbs,' 1849, p. 114.) They are furnished with some small muscles; one of
which, as I am informed by Prof. Turner, has been expressly described by
Theile as a rudimentary repetition of the extensor of the tail, a muscle
which is so largely developed in many mammals.
The spinal cord in man extends only as far downwards as the last dorsal or
first lumbar vertebra; but a thread-like structure (the filum terminale)
runs down the axis of the sacral part of the spinal canal, and even along
the back of the coccygeal bones. The upper part of this filament, as Prof.
Turner informs me, is undoubtedly homologous with the spinal cord; but the
lower part apparently consists merely of the pia mater, or vascular
investing membrane. Even in this case the os coccyx may be said to possess
a vestige of so important a structure as the spinal cord, though no longer
enclosed within a bony canal. The following fact, for which I am also
indebted to Prof. Turner, shews how closely the os coccyx corresponds with
the true tail in the lower animals: Luschka has recently discovered at the
extremity of the coccygeal bones a very peculiar convoluted body, which is
continuous with the middle sacral artery; and this discovery led Krause and
Meyer to examine the tail of a monkey (Macacus), and of a cat, in both of
which they found a similarly convoluted body, though not at the extremity.
The reproductive system offers various rudimentary structures; but these
differ in one important respect from the foregoing cases. Here we are not
concerned with the vestige of a part which does not belong to the species
in an efficient state, but with a part efficient in the one sex, and
represented in the other by a mere rudiment. Nevertheless, the occurrence
of such rudiments is as difficult to explain, on the belief of the separate
creation of each species, as in the foregoing cases. Hereafter I shall
have to recur to these rudiments, and shall shew that their presence
generally depends merely on inheritance, that is, on parts acquired by one
sex having been partially transmitted to the other. I will in this place
only give some instances of such rudiments. It is well known that in the
males of all mammals, including man, rudimentary mammae exist. These in
several instances have become well developed, and have yielded a copious
supply of milk. Their essential identity in the two sexes is likewise
shewn by their occasional sympathetic enlargement in both during an attack
of the measles. The vesicula prostatica, which has been observed in many
male mammals, is now universally acknowledged to be the homologue of the
female uterus, together with the connected passage. It is impossible to
read Leuckart's able description of this organ, and his reasoning, without
admitting the justness of his conclusion. This is especially clear in the
case of those mammals in which the true female uterus bifurcates, for in
the males of these the vesicula likewise bifurcates. (54. Leuckart, in
Todd's 'Cyclopaedia of Anatomy' 1849-52, vol. iv. p. 1415. In man this
organ is only from three to six lines in length, but, like so many other
rudimentary parts, it is variable in development as well as in other
characters.) Some other rudimentary structures belonging to the
reproductive system might have been here adduced. (55. See, on this
subject, Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 675, 676, 706.)
The bearing of the three great classes of facts now given is unmistakeable.
But it would be superfluous fully to recapitulate the line of argument
given in detail in my 'Origin of Species.' The homological construction of
the whole frame in the members of the same class is intelligible, if we
admit their descent from a common progenitor, together with their
subsequent adaptation to diversified conditions. On any other view, the
similarity of pattern between the hand of a man or monkey, the foot of a
horse, the flipper of a seal, the wing of a bat, etc., is utterly
inexplicable. (56. Prof. Bianconi, in a recently published work,
illustrated by admirable engravings ('La Theorie Darwinienne et la creation
dite independante,' 1874), endeavours to shew that homological structures,
in the above and other cases, can be fully explained on mechanical
principles, in accordance with their uses. No one has shewn so well, how
admirably such structures are adapted for their final purpose; and this
adaptation can, as I believe, be explained through natural selection. In
considering the wing of a bat, he brings forward (p. 218) what appears to
me (to use Auguste Comte's words) a mere metaphysical principle, namely,
the preservation "in its integrity of the mammalian nature of the animal."
In only a few cases does he discuss rudiments, and then only those parts
which are partially rudimentary, such as the little hoofs of the pig and
ox, which do not touch the ground; these he shews clearly to be of service
to the animal. It is unfortunate that he did not consider such cases as
the minute teeth, which never cut through the jaw in the ox, or the mammae
of male quadrupeds, or the wings of certain beetles, existing under the
soldered wing-covers, or the vestiges of the pistil and stamens in various
flowers, and many other such cases. Although I greatly admire Prof.
Bianconi's work, yet the belief now held by most naturalists seems to me
left unshaken, that homological structures are inexplicable on the
principle of mere adaptation.) It is no scientific explanation to assert
that they have all been formed on the same ideal plan. With respect to
development, we can clearly understand, on the principle of variations
supervening at a rather late embryonic period, and being inherited at a
corresponding period, how it is that the embryos of wonderfully different
forms should still retain, more or less perfectly, the structure of their
common progenitor. No other explanation has ever been given of the
marvellous fact that the embryos of a man, dog, seal, bat, reptile, etc.,
can at first hardly be distinguished from each other. In order to
understand the existence of rudimentary organs, we have only to suppose
that a former progenitor possessed the parts in question in a perfect
state, and that under changed habits of life they became greatly reduced,
either from simple disuse, or through the natural selection of those
individuals which were least encumbered with a superfluous part, aided by
the other means previously indicated.
Thus we can understand how it has come to pass that man and all other
vertebrate animals have been constructed on the same general model, why
they pass through the same early stages of development, and why they retain
certain rudiments in common. Consequently we ought frankly to admit their
community of descent: to take any other view, is to admit that our own
structure, and that of all the animals around us, is a mere snare laid to
entrap our judgment. This conclusion is greatly strengthened, if we look
to the members of the whole animal series, and consider the evidence
derived from their affinities or classification, their geographical
distribution and geological succession. It is only our natural prejudice,
and that arrogance which made our forefathers declare that they were
descended from demi-gods, which leads us to demur to this conclusion. But
the time will before long come, when it will be thought wonderful that
naturalists, who were well acquainted with the comparative structure and
development of man, and other mammals, should have believed that each was
the work of a separate act of creation.
CHAPTER II.
ON THE MANNER OF DEVELOPMENT OF MAN FROM SOME LOWER FORM.
Variability of body and mind in man--Inheritance--Causes of variability--
Laws of variation the same in man as in the lower animals--Direct action of
the conditions of life--Effects of the increased use and disuse of parts--
Arrested development--Reversion--Correlated variation--Rate of increase--
Checks to increase--Natural selection--Man the most dominant animal in the
world--Importance of his corporeal structure--The causes which have led to
his becoming erect--Consequent changes of structure--Decrease in size of
the canine teeth--Increased size and altered shape of the skull--Nakedness
--Absence of a tail--Defenceless condition of man.
It is manifest that man is now subject to much variability. No two
individuals of the same race are quite alike. We may compare millions of
faces, and each will be distinct. There is an equally great amount of
diversity in the proportions and dimensions of the various parts of the
body; the length of the legs being one of the most variable points. (1.
'Investigations in Military and Anthropological Statistics of American
Soldiers,' by B.A. Gould, 1869, p. 256.) Although in some quarters of the
world an elongated skull, and in other quarters a short skull prevails, yet
there is great diversity of shape even within the limits of the same race,
as with the aborigines of America and South Australia--the latter a race
"probably as pure and homogeneous in blood, customs, and language as any in
existence"--and even with the inhabitants of so confined an area as the
Sandwich Islands. (2. With respect to the "Cranial forms of the American
aborigines," see Dr. Aitken Meigs in 'Proc. Acad. Nat. Sci.' Philadelphia,
May 1868. On the Australians, see Huxley, in Lyell's 'Antiquity of Man,'
1863, p. 87. On the Sandwich Islanders, Prof. J. Wyman, 'Observations on
Crania,' Boston, 1868, p. 18.) An eminent dentist assures me that there is
nearly as much diversity in the teeth as in the features. The chief
arteries so frequently run in abnormal courses, that it has been found
useful for surgical purposes to calculate from 1040 corpses how often each
course prevails. (3. 'Anatomy of the Arteries,' by R. Quain. Preface,
vol. i. 1844.) The muscles are eminently variable: thus those of the foot
were found by Prof. Turner (4. 'Transactions of the Royal Society of
Edinburgh,' vol. xxiv. pp. 175, 189.) not to be strictly alike in any two
out of fifty bodies; and in some the deviations were considerable. He
adds, that the power of performing the appropriate movements must have been
modified in accordance with the several deviations. Mr. J. Wood has
recorded (5. 'Proceedings Royal Society,' 1867, p. 544; also 1868, pp.
483, 524. There is a previous paper, 1866, p. 229.) the occurrence of 295
muscular variations in thirty-six subjects, and in another set of the same
number no less than 558 variations, those occurring on both sides of the
body being only reckoned as one. In the last set, not one body out of the
thirty-six was "found totally wanting in departures from the standard
descriptions of the muscular system given in anatomical text books." A
single body presented the extraordinary number of twenty-five distinct
abnormalities. The same muscle sometimes varies in many ways: thus Prof.
Macalister describes (6. 'Proc. R. Irish Academy,' vol. x. 1868, p. 141.)
no less than twenty distinct variations in the palmaris accessorius.
The famous old anatomist, Wolff (7. 'Act. Acad. St. Petersburg,' 1778,
part ii. p. 217.), insists that the internal viscera are more variable than
the external parts: Nulla particula est quae non aliter et aliter in aliis
se habeat hominibus. He has even written a treatise on the choice of
typical examples of the viscera for representation. A discussion on the
beau-ideal of the liver, lungs, kidneys, etc., as of the human face divine,
sounds strange in our ears.
The variability or diversity of the mental faculties in men of the same
race, not to mention the greater differences between the men of distinct
races, is so notorious that not a word need here be said. So it is with
the lower animals. All who have had charge of menageries admit this fact,
and we see it plainly in our dogs and other domestic animals. Brehm
especially insists that each individual monkey of those which he kept tame
in Africa had its own peculiar disposition and temper: he mentions one
baboon remarkable for its high intelligence; and the keepers in the
Zoological Gardens pointed out to me a monkey, belonging to the New World
division, equally remarkable for intelligence. Rengger, also, insists on
the diversity in the various mental characters of the monkeys of the same
species which he kept in Paraguay; and this diversity, as he adds, is
partly innate, and partly the result of the manner in which they have been
treated or educated. (8. Brehm, 'Thierleben,' B. i. ss. 58, 87. Rengger,
'Saugethiere von Paraguay,' s. 57.)
I have elsewhere (9. 'Variation of Animals and Plants under
Domestication,' vol. ii. chap. xii.) so fully discussed the subject of
Inheritance, that I need here add hardly anything. A greater number of
facts have been collected with respect to the transmission of the most
trifling, as well as of the most important characters in man, than in any
of the lower animals; though the facts are copious enough with respect to
the latter. So in regard to mental qualities, their transmission is
manifest in our dogs, horses, and other domestic animals. Besides special
tastes and habits, general intelligence, courage, bad and good temper,
etc., are certainly transmitted. With man we see similar facts in almost
every family; and we now know, through the admirable labours of Mr. Galton
(10. 'Hereditary Genius: an Inquiry into its Laws and Consequences,'
1869.), that genius which implies a wonderfully complex combination of high
faculties, tends to be inherited; and, on the other hand, it is too certain
that insanity and deteriorated mental powers likewise run in families.
With respect to the causes of variability, we are in all cases very
ignorant; but we can see that in man as in the lower animals, they stand in
some relation to the conditions to which each species has been exposed,
during several generations. Domesticated animals vary more than those in a
state of nature; and this is apparently due to the diversified and changing
nature of the conditions to which they have been subjected. In this
respect the different races of man resemble domesticated animals, and so do
the individuals of the same race, when inhabiting a very wide area, like
that of America. We see the influence of diversified conditions in the
more civilised nations; for the members belonging to different grades of
rank, and following different occupations, present a greater range of
character than do the members of barbarous nations. But the uniformity of
savages has often been exaggerated, and in some cases can hardly be said to
exist. (11. Mr. Bates remarks ('The Naturalist on the Amazons,' 1863,
vol. ii p. 159), with respect to the Indians of the same South American
tribe, "no two of them were at all similar in the shape of the head; one
man had an oval visage with fine features, and another was quite Mongolian
in breadth and prominence of cheek, spread of nostrils, and obliquity of
eyes.") It is, nevertheless, an error to speak of man, even if we look
only to the conditions to which he has been exposed, as "far more
domesticated" (12. Blumenbach, 'Treatises on Anthropology.' Eng.
translat., 1865, p. 205.) than any other animal. Some savage races, such
as the Australians, are not exposed to more diversified conditions than are
many species which have a wide range. In another and much more important
respect, man differs widely from any strictly domesticated animal; for his
breeding has never long been controlled, either by methodical or
unconscious selection. No race or body of men has been so completely
subjugated by other men, as that certain individuals should be preserved,
and thus unconsciously selected, from somehow excelling in utility to their
masters. Nor have certain male and female individuals been intentionally
picked out and matched, except in the well-known case of the Prussian
grenadiers; and in this case man obeyed, as might have been expected, the
law of methodical selection; for it is asserted that many tall men were
reared in the villages inhabited by the grenadiers and their tall wives.
In Sparta, also, a form of selection was followed, for it was enacted that
all children should be examined shortly after birth; the well-formed and
vigorous being preserved, the others left to perish. (13. Mitford's
'History of Greece,' vol. i. p. 282. It appears also from a passage in
Xenophon's 'Memorabilia,' B. ii. 4 (to which my attention has been called
by the Rev. J.N. Hoare), that it was a well recognised principle with the
Greeks, that men ought to select their wives with a view to the health and
vigour of their children. The Grecian poet, Theognis, who lived 550 B.C.,
clearly saw how important selection, if carefully applied, would be for the
improvement of mankind. He saw, likewise, that wealth often checks the
proper action of sexual selection. He thus writes:
"With kine and horses, Kurnus! we proceed
By reasonable rules, and choose a breed
For profit and increase, at any price:
Of a sound stock, without defect or vice.
But, in the daily matches that we make,
The price is everything: for money's sake,
Men marry: women are in marriage given
The churl or ruffian, that in wealth has thriven,
May match his offspring with the proudest race:
Thus everything is mix'd, noble and base!
If then in outward manner, form, and mind,
You find us a degraded, motley kind,
Wonder no more, my friend! the cause is plain,
And to lament the consequence is vain."
(The Works of J. Hookham Frere, vol. ii. 1872, p. 334.))
If we consider all the races of man as forming a single species, his range
is enormous; but some separate races, as the Americans and Polynesians,
have very wide ranges. It is a well-known law that widely-ranging species
are much more variable than species with restricted ranges; and the
variability of man may with more truth be compared with that of widely-
ranging species, than with that of domesticated animals.
Not only does variability appear to be induced in man and the lower animals
by the same general causes, but in both the same parts of the body are
affected in a closely analogous manner. This has been proved in such full
detail by Godron and Quatrefages, that I need here only refer to their
works. (14. Godron, 'De l'Espece,' 1859, tom. ii. livre 3. Quatrefages,
'Unite de l'Espece Humaine,' 1861. Also Lectures on Anthropology, given in
the 'Revue des Cours Scientifiques,' 1866-1868.) Monstrosities, which
graduate into slight variations, are likewise so similar in man and the
lower animals, that the same classification and the same terms can be used
for both, as has been shewn by Isidore Geoffroy St.-Hilaire. (15. 'Hist.
Gen. et Part. des Anomalies de l'Organisation,' in three volumes, tom. i.
1832.) In my work on the variation of domestic animals, I have attempted
to arrange in a rude fashion the laws of variation under the following
heads:--The direct and definite action of changed conditions, as exhibited
by all or nearly all the individuals of the same species, varying in the
same manner under the same circumstances. The effects of the long-
continued use or disuse of parts. The cohesion of homologous parts. The
variability of multiple parts. Compensation of growth; but of this law I
have found no good instance in the case of man. The effects of the
mechanical pressure of one part on another; as of the pelvis on the cranium
of the infant in the womb. Arrests of development, leading to the
diminution or suppression of parts. The reappearance of long-lost
characters through reversion. And lastly, correlated variation. All these
so-called laws apply equally to man and the lower animals; and most of them
even to plants. It would be superfluous here to discuss all of them (16.
I have fully discussed these laws in my 'Variation of Animals and Plants
under Domestication,' vol. ii. chap. xxii. and xxiii. M. J.P. Durand has
lately (1868) published a valuable essay, 'De l'Influence des Milieux,'
etc. He lays much stress, in the case of plants, on the nature of the
soil.); but several are so important, that they must be treated at
considerable length.
THE DIRECT AND DEFINITE ACTION OF CHANGED CONDITIONS.
This is a most perplexing subject. It cannot be denied that changed
conditions produce some, and occasionally a considerable effect, on
organisms of all kinds; and it seems at first probable that if sufficient
time were allowed this would be the invariable result. But I have failed
to obtain clear evidence in favour of this conclusion; and valid reasons
may be urged on the other side, at least as far as the innumerable
structures are concerned, which are adapted for special ends. There can,
however, be no doubt that changed conditions induce an almost indefinite
amount of fluctuating variability, by which the whole organisation is
rendered in some degree plastic.
In the United States, above 1,000,000 soldiers, who served in the late war,
were measured, and the States in which they were born and reared were
recorded. (17. 'Investigations in Military and Anthrop. Statistics,'
etc., 1869, by B.A. Gould, pp. 93, 107, 126, 131, 134.) From this
astonishing number of observations it is proved that local influences of
some kind act directly on stature; and we further learn that "the State
where the physical growth has in great measure taken place, and the State
of birth, which indicates the ancestry, seem to exert a marked influence on
the stature." For instance, it is established, "that residence in the
Western States, during the years of growth, tends to produce increase of
stature." On the other hand, it is certain that with sailors, their life
delays growth, as shewn "by the great difference between the statures of
soldiers and sailors at the ages of seventeen and eighteen years." Mr.
B.A. Gould endeavoured to ascertain the nature of the influences which thus
act on stature; but he arrived only at negative results, namely that they
did not relate to climate, the elevation of the land, soil, nor even "in
any controlling degree" to the abundance or the need of the comforts of
life. This latter conclusion is directly opposed to that arrived at by
Villerme, from the statistics of the height of the conscripts in different
parts of France. When we compare the differences in stature between the
Polynesian chiefs and the lower orders within the same islands, or between
the inhabitants of the fertile volcanic and low barren coral islands of the
same ocean (18. For the Polynesians, see Prichard's 'Physical History of
Mankind,' vol. v. 1847, pp. 145, 283. Also Godron, 'De l'Espece,' tom. ii.
p. 289. There is also a remarkable difference in appearance between the
closely-allied Hindoos inhabiting the Upper Ganges and Bengal; see
Elphinstone's 'History of India,' vol. i. p. 324.) or again between the
Fuegians on the eastern and western shores of their country, where the
means of subsistence are very different, it is scarcely possible to avoid
the conclusion that better food and greater comfort do influence stature.
But the preceding statements shew how difficult it is to arrive at any
precise result. Dr. Beddoe has lately proved that, with the inhabitants of
Britain, residence in towns and certain occupations have a deteriorating
influence on height; and he infers that the result is to a certain extent
inherited, as is likewise the case in the United States. Dr. Beddoe
further believes that wherever a "race attains its maximum of physical
development, it rises highest in energy and moral vigour." (19. 'Memoirs,
Anthropological Society,' vol. iii. 1867-69, pp. 561, 565, 567.)
Whether external conditions produce any other direct effect on man is not
known. It might have been expected that differences of climate would have
had a marked influence, inasmuch as the lungs and kidneys are brought into
activity under a low temperature, and the liver and skin under a high one.
(20. Dr. Brakenridge, 'Theory of Diathesis,' 'Medical Times,' June 19 and
July 17, 1869.) It was formerly thought that the colour of the skin and
the character of the hair were determined by light or heat; and although it
can hardly be denied that some effect is thus produced, almost all
observers now agree that the effect has been very small, even after
exposure during many ages. But this subject will be more properly
discussed when we treat of the different races of mankind. With our
domestic animals there are grounds for believing that cold and damp
directly affect the growth of the hair; but I have not met with any
evidence on this head in the case of man.
EFFECTS OF THE INCREASED USE AND DISUSE OF PARTS.
It is well known that use strengthens the muscles in the individual, and
complete disuse, or the destruction of the proper nerve, weakens them.
When the eye is destroyed, the optic nerve often becomes atrophied. When
an artery is tied, the lateral channels increase not only in diameter, but
in the thickness and strength of their coats. When one kidney ceases to
act from disease, the other increases in size, and does double work. Bones
increase not only in thickness, but in length, from carrying a greater
weight. (21. I have given authorities for these several statements in my
'Variation of Animals and Plants under Domestication,' vol. ii. pp. 297-
300. Dr. Jaeger, "Uber das Langenwachsthum der Knochen," 'Jenaischen
Zeitschrift,' B. v. Heft. i.) Different occupations, habitually followed,
lead to changed proportions in various parts of the body. Thus it was
ascertained by the United States Commission (22. 'Investigations,' etc.,
by B.A. Gould, 1869, p. 288.) that the legs of the sailors employed in the
late war were longer by 0.217 of an inch than those of the soldiers, though
the sailors were on an average shorter men; whilst their arms were shorter
by 1.09 of an inch, and therefore, out of proportion, shorter in relation
to their lesser height. This shortness of the arms is apparently due to
their greater use, and is an unexpected result: but sailors chiefly use
their arms in pulling, and not in supporting weights. With sailors, the
girth of the neck and the depth of the instep are greater, whilst the
circumference of the chest, waist, and hips is less, than in soldiers.
Whether the several foregoing modifications would become hereditary, if the
same habits of life were followed during many generations, is not known,
but it is probable. Rengger (23. 'Saugethiere von Paraguay,' 1830, s. 4.)
attributes the thin legs and thick arms of the Payaguas Indians to
successive generations having passed nearly their whole lives in canoes,
with their lower extremities motionless. Other writers have come to a
similar conclusion in analogous cases. According to Cranz (24. 'History
of Greenland,' Eng. translat., 1767, vol. i. p. 230.), who lived for a long
time with the Esquimaux, "the natives believe that ingenuity and dexterity
in seal-catching (their highest art and virtue) is hereditary; there is
really something in it, for the son of a celebrated seal-catcher will
distinguish himself, though he lost his father in childhood." But in this
case it is mental aptitude, quite as much as bodily structure, which
appears to be inherited. It is asserted that the hands of English
labourers are at birth larger than those of the gentry. (25.
'Intermarriage,' by Alex. Walker, 1838, p. 377.) From the correlation
which exists, at least in some cases (26. 'The Variation of Animals under
Domestication,' vol. i. p. 173.), between the development of the
extremities and of the jaws, it is possible that in those classes which do
not labour much with their hands and feet, the jaws would be reduced in
size from this cause. That they are generally smaller in refined and
civilised men than in hard-working men or savages, is certain. But with
savages, as Mr. Herbert Spencer (27. 'Principles of Biology,' vol. i. p.
455.) has remarked, the greater use of the jaws in chewing coarse, uncooked
food, would act in a direct manner on the masticatory muscles, and on the
bones to which they are attached. In infants, long before birth, the skin
on the soles of the feet is thicker than on any other part of the body;
(28. Paget, 'Lectures on Surgical Pathology,' vol. ii, 1853, p. 209.) and
it can hardly be doubted that this is due to the inherited effects of
pressure during a long series of generations.
It is familiar to every one that watchmakers and engravers are liable to be
short-sighted, whilst men living much out of doors, and especially savages,
are generally long-sighted. (29. It is a singular and unexpected fact
that sailors are inferior to landsmen in their mean distance of distinct
vision. Dr. B.A. Gould ('Sanitary Memoirs of the War of the Rebellion,'
1869, p. 530), has proved this to be the case; and he accounts for it by
the ordinary range of vision in sailors being "restricted to the length of
the vessel and the height of the masts.") Short-sight and long-sight
certainly tend to be inherited. (30. 'The Variation of Animals under
Domestication,' vol. i. p. 8.) The inferiority of Europeans, in comparison
with savages, in eyesight and in the other senses, is no doubt the
accumulated and transmitted effect of lessened use during many generations;
for Rengger (31. 'Saugethiere von Paraguay,' s. 8, 10. I have had good
opportunities for observing the extraordinary power of eyesight in the
Fuegians. See also Lawrence ('Lectures on Physiology,' etc., 1822, p. 404)
on this same subject. M. Giraud-Teulon has recently collected ('Revue des
Cours Scientifiques,' 1870, p. 625) a large and valuable body of evidence
proving that the cause of short-sight, "C'est le travail assidu, de pres.")
states that he has repeatedly observed Europeans, who had been brought up
and spent their whole lives with the wild Indians, who nevertheless did not
equal them in the sharpness of their senses. The same naturalist observes
that the cavities in the skull for the reception of the several sense-
organs are larger in the American aborigines than in Europeans; and this
probably indicates a corresponding difference in the dimensions of the
organs themselves. Blumenbach has also remarked on the large size of the
nasal cavities in the skulls of the American aborigines, and connects this
fact with their remarkably acute power of smell. The Mongolians of the
plains of northern Asia, according to Pallas, have wonderfully perfect
senses; and Prichard believes that the great breadth of their skulls across
the zygomas follows from their highly-developed sense organs. (32.
Prichard, 'Physical History of Mankind,' on the authority of Blumenbach,
vol. i. 1851, p. 311; for the statement by Pallas, vol. iv. 1844, p. 407.)
The Quechua Indians inhabit the lofty plateaux of Peru; and Alcide
d'Orbigny states (33. Quoted by Prichard, 'Researches into the Physical
History of Mankind,' vol. v. p. 463.) that, from continually breathing a
highly rarefied atmosphere, they have acquired chests and lungs of
extraordinary dimensions. The cells, also, of the lungs are larger and
more numerous than in Europeans. These observations have been doubted, but
Mr. D. Forbes carefully measured many Aymaras, an allied race, living at
the height of between 10,000 and 15,000 feet; and he informs me (34. Mr.
Forbes' valuable paper is now published in the 'Journal of the Ethnological
Society of London,' new series, vol. ii. 1870, p.193.) that they differ
conspicuously from the men of all other races seen by him in the
circumference and length of their bodies. In his table of measurements,
the stature of each man is taken at 1000, and the other measurements are
reduced to this standard. It is here seen that the extended arms of the
Aymaras are shorter than those of Europeans, and much shorter than those of
Negroes. The legs are likewise shorter; and they present this remarkable
peculiarity, that in every Aymara measured, the femur is actually shorter
than the tibia. On an average, the length of the femur to that of the
tibia is as 211 to 252; whilst in two Europeans, measured at the same time,
the femora to the tibiae were as 244 to 230; and in three Negroes as 258 to
241. The humerus is likewise shorter relatively to the forearm. This
shortening of that part of the limb which is nearest to the body, appears
to be, as suggested to me by Mr. Forbes, a case of compensation in relation
with the greatly increased length of the trunk. The Aymaras present some
other singular points of structure, for instance, the very small projection
of the heel.
These men are so thoroughly acclimatised to their cold and lofty abode,
that when formerly carried down by the Spaniards to the low eastern plains,
and when now tempted down by high wages to the gold-washings, they suffer a
frightful rate of mortality. Nevertheless Mr. Forbes found a few pure
families which had survived during two generations: and he observed that
they still inherited their characteristic peculiarities. But it was
manifest, even without measurement, that these peculiarities had all
decreased; and on measurement, their bodies were found not to be so much
elongated as those of the men on the high plateau; whilst their femora had
become somewhat lengthened, as had their tibiae, although in a less degree.
The actual measurements may be seen by consulting Mr. Forbes's memoir.
From these observations, there can, I think, be no doubt that residence
during many generations at a great elevation tends, both directly and
indirectly, to induce inherited modifications in the proportions of the
body. (35. Dr. Wilckens ('Landwirthschaft. Wochenblatt,' No. 10, 1869)
has lately published an interesting essay shewing how domestic animals,
which live in mountainous regions, have their frames modified.)
Although man may not have been much modified during the latter stages of
his existence through the increased or decreased use of parts, the facts
now given shew that his liability in this respect has not been lost; and we
positively know that the same law holds good with the lower animals.
Consequently we may infer that when at a remote epoch the progenitors of
man were in a transitional state, and were changing from quadrupeds into
bipeds, natural selection would probably have been greatly aided by the
inherited effects of the increased or diminished use of the different parts
of the body.
ARRESTS OF DEVELOPMENT.
There is a difference between arrested development and arrested growth, for
parts in the former state continue to grow whilst still retaining their
early condition. Various monstrosities come under this head; and some, as
a cleft palate, are known to be occasionally inherited. It will suffice
for our purpose to refer to the arrested brain-development of
microcephalous idiots, as described in Vogt's memoir. (36. 'Memoires sur
les Microcephales,' 1867, pp. 50, 125, 169, 171, 184-198.) Their skulls
are smaller, and the convolutions of the brain are less complex than in
normal men. The frontal sinus, or the projection over the eye-brows, is
largely developed, and the jaws are prognathous to an "effrayant" degree;
so that these idiots somewhat resemble the lower types of mankind. Their
intelligence, and most of their mental faculties, are extremely feeble.
They cannot acquire the power of speech, and are wholly incapable of
prolonged attention, but are much given to imitation. They are strong and
remarkably active, continually gambolling and jumping about, and making
grimaces. They often ascend stairs on all-fours; and are curiously fond of
climbing up furniture or trees. We are thus reminded of the delight shewn
by almost all boys in climbing trees; and this again reminds us how lambs
and kids, originally alpine animals, delight to frisk on any hillock,
however small. Idiots also resemble the lower animals in some other
respects; thus several cases are recorded of their carefully smelling every
mouthful of food before eating it. One idiot is described as often using
his mouth in aid of his hands, whilst hunting for lice. They are often
filthy in their habits, and have no sense of decency; and several cases
have been published of their bodies being remarkably hairy. (37. Prof.
Laycock sums up the character of brute-like idiots by calling them
"theroid;" 'Journal of Mental Science,' July 1863. Dr. Scott ('The Deaf
and Dumb,' 2nd ed. 1870, p. 10) has often observed the imbecile smelling
their food. See, on this same subject, and on the hairiness of idiots, Dr.
Maudsley, 'Body and Mind,' 1870, pp. 46-51. Pinel has also given a
striking case of hairiness in an idiot.)
REVERSION.
Many of the cases to be here given, might have been introduced under the
last heading. When a structure is arrested in its development, but still
continues growing, until it closely resembles a corresponding structure in
some lower and adult member of the same group, it may in one sense be
considered as a case of reversion. The lower members in a group give us
some idea how the common progenitor was probably constructed; and it is
hardly credible that a complex part, arrested at an early phase of
embryonic development, should go on growing so as ultimately to perform its
proper function, unless it had acquired such power during some earlier
state of existence, when the present exceptional or arrested structure was
normal. The simple brain of a microcephalous idiot, in as far as it
resembles that of an ape, may in this sense be said to offer a case of
reversion. (38. In my 'Variation of Animals under Domestication' (vol.
ii. p. 57), I attributed the not very rare cases of supernumerary mammae in
women to reversion. I was led to this as a probable conclusion, by the
additional mammae being generally placed symmetrically on the breast; and
more especially from one case, in which a single efficient mamma occurred
in the inguinal region of a woman, the daughter of another woman with
supernumerary mammae. But I now find (see, for instance, Prof. Preyer,
'Der Kampf um das Dasein,' 1869, s. 45) that mammae erraticae, occur in
other situations, as on the back, in the armpit, and on the thigh; the
mammae in this latter instance having given so much milk that the child was
thus nourished. The probability that the additional mammae are due to
reversion is thus much weakened; nevertheless, it still seems to me
probable, because two pairs are often found symmetrically on the breast;
and of this I myself have received information in several cases. It is
well known that some Lemurs normally have two pairs of mammae on the
breast. Five cases have been recorded of the presence of more than a pair
of mammae (of course rudimentary) in the male sex of mankind; see 'Journal
of Anat. and Physiology,' 1872, p. 56, for a case given by Dr. Handyside,
in which two brothers exhibited this peculiarity; see also a paper by Dr.
Bartels, in 'Reichert's and du Bois-Reymond's Archiv.,' 1872, p. 304. In
one of the cases alluded to by Dr. Bartels, a man bore five mammae, one
being medial and placed above the navel; Meckel von Hemsbach thinks that
this latter case is illustrated by a medial mamma occurring in certain
Cheiroptera. On the whole, we may well doubt if additional mammae would
ever have been developed in both sexes of mankind, had not his early
progenitors been provided with more than a single pair.
In the above work (vol. ii. p. 12), I also attributed, though with much
hesitation, the frequent cases of polydactylism in men and various animals
to reversion. I was partly led to this through Prof. Owen's statement,
that some of the Ichthyopterygia possess more than five digits, and
therefore, as I supposed, had retained a primordial condition; but Prof.
Gegenbaur ('Jenaischen Zeitschrift,' B. v. Heft 3, s. 341), disputes Owen's
conclusion. On the other hand, according to the opinion lately advanced by
Dr. Gunther, on the paddle of Ceratodus, which is provided with articulated
bony rays on both sides of a central chain of bones, there seems no great
difficulty in admitting that six or more digits on one side, or on both
sides, might reappear through reversion. I am informed by Dr. Zouteveen
that there is a case on record of a man having twenty-four fingers and
twenty-four toes! I was chiefly led to the conclusion that the presence of
supernumerary digits might be due to reversion from the fact that such
digits, not only are strongly inherited, but, as I then believed, had the
power of regrowth after amputation, like the normal digits of the lower
vertebrata. But I have explained in the second edition of my Variation
under Domestication why I now place little reliance on the recorded cases
of such regrowth. Nevertheless it deserves notice, inasmuch as arrested
development and reversion are intimately related processes; that various
structures in an embryonic or arrested condition, such as a cleft palate,
bifid uterus, etc., are frequently accompanied by polydactylism. This has
been strongly insisted on by Meckel and Isidore Geoffroy St.-Hilaire. But
at present it is the safest course to give up altogether the idea that
there is any relation between the development of supernumerary digits and
reversion to some lowly organised progenitor of man.) There are other
cases which come more strictly under our present head of reversion.
Certain structures, regularly occurring in the lower members of the group
to which man belongs, occasionally make their appearance in him, though not
found in the normal human embryo; or, if normally present in the human
embryo, they become abnormally developed, although in a manner which is
normal in the lower members of the group. These remarks will be rendered
clearer by the following illustrations.
In various mammals the uterus graduates from a double organ with two
distinct orifices and two passages, as in the marsupials, into a single
organ, which is in no way double except from having a slight internal fold,
as in the higher apes and man. The rodents exhibit a perfect series of
gradations between these two extreme states. In all mammals the uterus is
developed from two simple primitive tubes, the inferior portions of which
form the cornua; and it is in the words of Dr. Farre, "by the coalescence
of the two cornua at their lower extremities that the body of the uterus is
formed in man; while in those animals in which no middle portion or body
exists, the cornua remain ununited. As the development of the uterus
proceeds, the two cornua become gradually shorter, until at length they are
lost, or, as it were, absorbed into the body of the uterus." The angles of
the uterus are still produced into cornua, even in animals as high up in
the scale as the lower apes and lemurs.
Now in women, anomalous cases are not very infrequent, in which the mature
uterus is furnished with cornua, or is partially divided into two organs;
and such cases, according to Owen, repeat "the grade of concentrative
development," attained by certain rodents. Here perhaps we have an
instance of a simple arrest of embryonic development, with subsequent
growth and perfect functional development; for either side of the partially
double uterus is capable of performing the proper office of gestation. In
other and rarer cases, two distinct uterine cavities are formed, each
having its proper orifice and passage. (39. See Dr. A. Farre's well-known
article in the 'Cyclopaedia of Anatomy and Physiology,' vol. v. 1859, p.
642. Owen, 'Anatomy of Vertebrates,' vol. iii. 1868, p. 687. Professor
Turner, in 'Edinburgh Medical Journal,' February, 1865.) No such stage is
passed through during the ordinary development of the embryo; and it is
difficult to believe, though perhaps not impossible, that the two simple,
minute, primitive tubes should know how (if such an expression may be used)
to grow into two distinct uteri, each with a well-constructed orifice and
passage, and each furnished with numerous muscles, nerves, glands and
vessels, if they had not formerly passed through a similar course of
development, as in the case of existing marsupials. No one will pretend
that so perfect a structure as the abnormal double uterus in woman could be
the result of mere chance. But the principle of reversion, by which a
long-lost structure is called back into existence, might serve as the guide
for its full development, even after the lapse of an enormous interval of
time.
Professor Canestrini, after discussing the foregoing and various analogous
cases, arrives at the same conclusion as that just given. He adduces
another instance, in the case of the malar bone (40. 'Annuario della Soc.
dei Naturalisti,' Modena, 1867, p. 83. Prof. Canestrini gives extracts on
this subject from various authorities. Laurillard remarks, that as he has
found a complete similarity in the form, proportions, and connection of the
two malar bones in several human subjects and in certain apes, he cannot
consider this disposition of the parts as simply accidental. Another paper
on this same anomaly has been published by Dr. Saviotti in the 'Gazzetta
delle Cliniche,' Turin, 1871, where he says that traces of the division may
be detected in about two per cent. of adult skulls; he also remarks that it
more frequently occurs in prognathous skulls, not of the Aryan race, than
in others. See also G. Delorenzi on the same subject; 'Tre nuovi casi
d'anomalia dell' osso malare,' Torino, 1872. Also, E. Morselli, 'Sopra una
rara anomalia dell' osso malare,' Modena, 1872. Still more recently Gruber
has written a pamphlet on the division of this bone. I give these
references because a reviewer, without any grounds or scruples, has thrown
doubts on my statements.), which, in some of the Quadrumana and other
mammals, normally consists of two portions. This is its condition in the
human foetus when two months old; and through arrested development, it
sometimes remains thus in man when adult, more especially in the lower
prognathous races. Hence Canestrini concludes that some ancient progenitor
of man must have had this bone normally divided into two portions, which
afterwards became fused together. In man the frontal bone consists of a
single piece, but in the embryo, and in children, and in almost all the
lower mammals, it consists of two pieces separated by a distinct suture.
This suture occasionally persists more or less distinctly in man after
maturity; and more frequently in ancient than in recent crania, especially,
as Canestrini has observed, in those exhumed from the Drift, and belonging
to the brachycephalic type. Here again he comes to the same conclusion as
in the analogous case of the malar bones. In this, and other instances
presently to be given, the cause of ancient races approaching the lower
animals in certain characters more frequently than do the modern races,
appears to be, that the latter stand at a somewhat greater distance in the
long line of descent from their early semi-human progenitors.
Various other anomalies in man, more or less analogous to the foregoing,
have been advanced by different authors, as cases of reversion; but these
seem not a little doubtful, for we have to descend extremely low in the
mammalian series, before we find such structures normally present. (41. A
whole series of cases is given by Isidore Geoffroy St.-Hilaire, 'Hist. des
Anomalies,' tom, iii, p. 437. A reviewer ('Journal of Anatomy and
Physiology,' 1871, p. 366) blames me much for not having discussed the
numerous cases, which have been recorded, of various parts arrested in
their development. He says that, according to my theory, "every transient
condition of an organ, during its development, is not only a means to an
end, but once was an end in itself." This does not seem to me necessarily
to hold good. Why should not variations occur during an early period of
development, having no relation to reversion; yet such variations might be
preserved and accumulated, if in any way serviceable, for instance, in
shortening and simplifying the course of development? And again, why
should not injurious abnormalities, such as atrophied or hypertrophied
parts, which have no relation to a former state of existence, occur at an
early period, as well as during maturity?)
In man, the canine teeth are perfectly efficient instruments for
mastication. But their true canine character, as Owen (42. 'Anatomy of
Vertebrates,' vol. iii. 1868, p. 323.) remarks, "is indicated by the
conical form of the crown, which terminates in an obtuse point, is convex
outward and flat or sub-concave within, at the base of which surface there
is a feeble prominence. The conical form is best expressed in the Melanian
races, especially the Australian. The canine is more deeply implanted, and
by a stronger fang than the incisors." Nevertheless, this tooth no longer
serves man as a special weapon for tearing his enemies or prey; it may,
therefore, as far as its proper function is concerned, be considered as
rudimentary. In every large collection of human skulls some may be found,
as Haeckel (43. 'Generelle Morphologie,' 1866, B. ii. s. clv.) observes,
with the canine teeth projecting considerably beyond the others in the same
manner as in the anthropomorphous apes, but in a less degree. In these
cases, open spaces between the teeth in the one jaw are left for the
reception of the canines of the opposite jaw. An inter-space of this kind
in a Kaffir skull, figured by Wagner, is surprisingly wide. (44. Carl
Vogt's 'Lectures on Man,' Eng. translat., 1864, p. 151.) Considering how
few are the ancient skulls which have been examined, compared to recent
skulls, it is an interesting fact that in at least three cases the canines
project largely; and in the Naulette jaw they are spoken of as enormous.
(45. C. Carter Blake, on a jaw from La Naulette, 'Anthropological Review,'
1867, p. 295. Schaaffhausen, ibid. 1868, p. 426.)
Of the anthropomorphous apes the males alone have their canines fully
developed; but in the female gorilla, and in a less degree in the female
orang, these teeth project considerably beyond the others; therefore the
fact, of which I have been assured, that women sometimes have considerably
projecting canines, is no serious objection to the belief that their
occasional great development in man is a case of reversion to an ape-like
progenitor. He who rejects with scorn the belief that the shape of his own
canines, and their occasional great development in other men, are due to
our early forefathers having been provided with these formidable weapons,
will probably reveal, by sneering, the line of his descent. For though he
no longer intends, nor has the power, to use these teeth as weapons, he
will unconsciously retract his "snarling muscles" (thus named by Sir C.
Bell) (46. The Anatomy of Expression, 1844, pp. 110, 131.), so as to
expose them ready for action, like a dog prepared to fight.
Many muscles are occasionally developed in man, which are proper to the
Quadrumana or other mammals. Professor Vlacovich (47. Quoted by Prof.
Canestrini in the 'Annuario della Soc. dei Naturalisti,' 1867, p. 90.)
examined forty male subjects, and found a muscle, called by him the ischio-
pubic, in nineteen of them; in three others there was a ligament which
represented this muscle; and in the remaining eighteen no trace of it. In
only two out of thirty female subjects was this muscle developed on both
sides, but in three others the rudimentary ligament was present. This
muscle, therefore, appears to be much more common in the male than in the
female sex; and on the belief in the descent of man from some lower form,
the fact is intelligible; for it has been detected in several of the lower
animals, and in all of these it serves exclusively to aid the male in the
act of reproduction.
Mr. J. Wood, in his valuable series of papers (48. These papers deserve
careful study by any one who desires to learn how frequently our muscles
vary, and in varying come to resemble those of the Quadrumana. The
following references relate to the few points touched on in my text:
'Proc. Royal Soc.' vol. xiv. 1865, pp. 379-384; vol. xv. 1866, pp. 241,
242; vol. xv. 1867, p. 544; vol. xvi. 1868, p. 524. I may here add that
Dr. Murie and Mr. St. George Mivart have shewn in their Memoir on the
Lemuroidea ('Transactions, Zoological Society,' vol. vii. 1869, p. 96), how
extraordinarily variable some of the muscles are in these animals, the
lowest members of the Primates. Gradations, also, in the muscles leading
to structures found in animals still lower in the scale, are numerous in
the Lemuroidea.), has minutely described a vast number of muscular
variations in man, which resemble normal structures in the lower animals.
The muscles which closely resemble those regularly present in our nearest
allies, the Quadrumana, are too numerous to be here even specified. In a
single male subject, having a strong bodily frame, and well-formed skull,
no less than seven muscular variations were observed, all of which plainly
represented muscles proper to various kinds of apes. This man, for
instance, had on both sides of his neck a true and powerful "levator
claviculae," such as is found in all kinds of apes, and which is said to
occur in about one out of sixty human subjects. (49. See also Prof.
Macalister in 'Proceedings, Royal Irish Academy,' vol. x. 1868, p. 124.)
Again, this man had "a special abductor of the metatarsal bone of the fifth
digit, such as Professor Huxley and Mr. Flower have shewn to exist
uniformly in the higher and lower apes." I will give only two additional
cases; the acromio-basilar muscle is found in all mammals below man, and
seems to be correlated with a quadrupedal gait, (50. Mr. Champneys in
'Journal of Anatomy and Physiology,' Nov. 1871, p. 178.) and it occurs in
about one out of sixty human subjects. In the lower extremities Mr.
Bradley (51. Ibid. May 1872, p. 421.) found an abductor ossis metatarsi
quinti in both feet of man; this muscle had not up to that time been
recorded in mankind, but is always present in the anthropomorphous apes.
The muscles of the hands and arms--parts which are so eminently
characteristic of man--are extremely liable to vary, so as to resemble the
corresponding muscles in the lower animals. (52. Prof. Macalister (ibid.
p. 121) has tabulated his observations, and finds that muscular
abnormalities are most frequent in the fore-arms, secondly, in the face,
thirdly, in the foot, etc.) Such resemblances are either perfect or
imperfect; yet in the latter case they are manifestly of a transitional
nature. Certain variations are more common in man, and others in woman,
without our being able to assign any reason. Mr. Wood, after describing
numerous variations, makes the following pregnant remark. "Notable
departures from the ordinary type of the muscular structures run in grooves
or directions, which must be taken to indicate some unknown factor, of much
importance to a comprehensive knowledge of general and scientific anatomy."
(53. The Rev. Dr. Haughton, after giving ('Proc. R. Irish Academy,' June
27, 1864, p. 715) a remarkable case of variation in the human flexor
pollicis longus, adds, "This remarkable example shews that man may
sometimes possess the arrangement of tendons of thumb and fingers
characteristic of the macaque; but whether such a case should be regarded
as a macaque passing upwards into a man, or a man passing downwards into a
macaque, or as a congenital freak of nature, I cannot undertake to say."
It is satisfactory to hear so capable an anatomist, and so embittered an
opponent of evolutionism, admitting even the possibility of either of his
first propositions. Prof. Macalister has also described ('Proceedings
Royal Irish Academy,' vol. x. 1864, p. 138) variations in the flexor
pollicis longus, remarkable from their relations to the same muscle in the
Quadrumana.)
That this unknown factor is reversion to a former state of existence may be
admitted as in the highest degree probable. (54. Since the first edition
of this book appeared, Mr. Wood has published another memoir in the
Philosophical Transactions, 1870, p. 83, on the varieties of the muscles of
the human neck, shoulder, and chest. He here shews how extremely variable
these muscles are, and how often and how closely the variations resemble
the normal muscles of the lower animals. He sums up by remarking, "It will
be enough for my purpose if I have succeeded in shewing the more important
forms which, when occurring as varieties in the human subject, tend to
exhibit in a sufficiently marked manner what may be considered as proofs
and examples of the Darwinian principle of reversion, or law of
inheritance, in this department of anatomical science.") It is quite
incredible that a man should through mere accident abnormally resemble
certain apes in no less than seven of his muscles, if there had been no
genetic connection between them. On the other hand, if man is descended
from some ape-like creature, no valid reason can be assigned why certain
muscles should not suddenly reappear after an interval of many thousand
generations, in the same manner as with horses, asses, and mules, dark-
coloured stripes suddenly reappear on the legs, and shoulders, after an
interval of hundreds, or more probably of thousands of generations.
These various cases of reversion are so closely related to those of
rudimentary organs given in the first chapter, that many of them might have
been indifferently introduced either there or here. Thus a human uterus
furnished with cornua may be said to represent, in a rudimentary condition,
the same organ in its normal state in certain mammals. Some parts which
are rudimentary in man, as the os coccyx in both sexes, and the mammae in
the male sex, are always present; whilst others, such as the supracondyloid
foramen, only occasionally appear, and therefore might have been introduced
under the head of reversion. These several reversionary structures, as
well as the strictly rudimentary ones, reveal the descent of man from some
lower form in an unmistakable manner.
CORRELATED VARIATION.
In man, as in the lower animals, many structures are so intimately related,
that when one part varies so does another, without our being able, in most
cases, to assign any reason. We cannot say whether the one part governs
the other, or whether both are governed by some earlier developed part.
Various monstrosities, as I. Geoffroy repeatedly insists, are thus
intimately connected. Homologous structures are particularly liable to
change together, as we see on the opposite sides of the body, and in the
upper and lower extremities. Meckel long ago remarked, that when the
muscles of the arm depart from their proper type, they almost always
imitate those of the leg; and so, conversely, with the muscles of the legs.
The organs of sight and hearing, the teeth and hair, the colour of the skin
and of the hair, colour and constitution, are more or less correlated.
(55. The authorities for these several statements are given in my
'Variation of Animals under Domestication,' vol. ii. pp. 320-335.)
Professor Schaaffhausen first drew attention to the relation apparently
existing between a muscular frame and the strongly-pronounced supra-orbital
ridges, which are so characteristic of the lower races of man.
Besides the variations which can be grouped with more or less probability
under the foregoing heads, there is a large class of variations which may
be provisionally called spontaneous, for to our ignorance they appear to
arise without any exciting cause. It can, however, be shewn that such
variations, whether consisting of slight individual differences, or of
strongly-marked and abrupt deviations of structure, depend much more on the
constitution of the organism than on the nature of the conditions to which
it has been subjected. (56. This whole subject has been discussed in
chap. xxiii. vol. ii. of my 'Variation of Animals and Plants under
Domestication.')
RATE OF INCREASE.
Civilised populations have been known under favourable conditions, as in
the United States, to double their numbers in twenty-five years; and,
according to a calculation, by Euler, this might occur in a little over
twelve years. (57. See the ever memorable 'Essay on the Principle of
Population,' by the Rev. T. Malthus, vol. i. 1826. pp. 6, 517.) At the
former rate, the present population of the United States (thirty millions),
would in 657 years cover the whole terraqueous globe so thickly, that four
men would have to stand on each square yard of surface. The primary or
fundamental check to the continued increase of man is the difficulty of
gaining subsistence, and of living in comfort. We may infer that this is
the case from what we see, for instance, in the United States, where
subsistence is easy, and there is plenty of room. If such means were
suddenly doubled in Great Britain, our number would be quickly doubled.
With civilised nations this primary check acts chiefly by restraining
marriages. The greater death-rate of infants in the poorest classes is
also very important; as well as the greater mortality, from various
diseases, of the inhabitants of crowded and miserable houses, at all ages.
The effects of severe epidemics and wars are soon counterbalanced, and more
than counterbalanced, in nations placed under favourable conditions.
Emigration also comes in aid as a temporary check, but, with the extremely
poor classes, not to any great extent.
There is reason to suspect, as Malthus has remarked, that the reproductive
power is actually less in barbarous, than in civilised races. We know
nothing positively on this head, for with savages no census has been taken;
but from the concurrent testimony of missionaries, and of others who have
long resided with such people, it appears that their families are usually
small, and large ones rare. This may be partly accounted for, as it is
believed, by the women suckling their infants during a long time; but it is
highly probable that savages, who often suffer much hardship, and who do
not obtain so much nutritious food as civilised men, would be actually less
prolific. I have shewn in a former work (58. 'Variation of Animals and
Plants under Domestication,' vol ii. pp. 111-113, 163.), that all our
domesticated quadrupeds and birds, and all our cultivated plants, are more
fertile than the corresponding species in a state of nature. It is no
valid objection to this conclusion that animals suddenly supplied with an
excess of food, or when grown very fat; and that most plants on sudden
removal from very poor to very rich soil, are rendered more or less
sterile. We might, therefore, expect that civilised men, who in one sense
are highly domesticated, would be more prolific than wild men. It is also
probable that the increased fertility of civilised nations would become, as
with our domestic animals, an inherited character: it is at least known
that with mankind a tendency to produce twins runs in families. (59. Mr.
Sedgwick, 'British and Foreign Medico-Chirurgical Review,' July 1863, p.
170.)
Notwithstanding that savages appear to be less prolific than civilised
people, they would no doubt rapidly increase if their numbers were not by
some means rigidly kept down. The Santali, or hill-tribes of India, have
recently afforded a good illustration of this fact; for, as shewn by Mr.
Hunter (60. 'The Annals of Rural Bengal,' by W.W. Hunter, 1868, p. 259.),
they have increased at an extraordinary rate since vaccination has been
introduced, other pestilences mitigated, and war sternly repressed. This
increase, however, would not have been possible had not these rude people
spread into the adjoining districts, and worked for hire. Savages almost
always marry; yet there is some prudential restraint, for they do not
commonly marry at the earliest possible age. The young men are often
required to shew that they can support a wife; and they generally have
first to earn the price with which to purchase her from her parents. With
savages the difficulty of obtaining subsistence occasionally limits their
number in a much more direct manner than with civilised people, for all
tribes periodically suffer from severe famines. At such times savages are
forced to devour much bad food, and their health can hardly fail to be
injured. Many accounts have been published of their protruding stomachs
and emaciated limbs after and during famines. They are then, also,
compelled to wander much, and, as I was assured in Australia, their infants
perish in large numbers. As famines are periodical, depending chiefly on
extreme seasons, all tribes must fluctuate in number. They cannot steadily
and regularly increase, as there is no artificial increase in the supply of
food. Savages, when hard pressed, encroach on each other's territories,
and war is the result; but they are indeed almost always at war with their
neighbours. They are liable to many accidents on land and water in their
search for food; and in some countries they suffer much from the larger
beasts of prey. Even in India, districts have been depopulated by the
ravages of tigers.
Malthus has discussed these several checks, but he does not lay stress
enough on what is probably the most important of all, namely infanticide,
especially of female infants, and the habit of procuring abortion. These
practices now prevail in many quarters of the world; and infanticide seems
formerly to have prevailed, as Mr. M'Lennan (61. 'Primitive Marriage,'
1865.) has shewn, on a still more extensive scale. These practices appear
to have originated in savages recognising the difficulty, or rather the
impossibility of supporting all the infants that are born. Licentiousness
may also be added to the foregoing checks; but this does not follow from
failing means of subsistence; though there is reason to believe that in
some cases (as in Japan) it has been intentionally encouraged as a means of
keeping down the population.
If we look back to an extremely remote epoch, before man had arrived at the
dignity of manhood, he would have been guided more by instinct and less by
reason than are the lowest savages at the present time. Our early semi-
human progenitors would not have practised infanticide or polyandry; for
the instincts of the lower animals are never so perverted (62. A writer in
the 'Spectator' (March 12, 1871, p. 320) comments as follows on this
passage:--"Mr. Darwin finds himself compelled to reintroduce a new doctrine
of the fall of man. He shews that the instincts of the higher animals are
far nobler than the habits of savage races of men, and he finds himself,
therefore, compelled to re-introduce,--in a form of the substantial
orthodoxy of which he appears to be quite unconscious,--and to introduce as
a scientific hypothesis the doctrine that man's gain of KNOWLEDGE was the
cause of a temporary but long-enduring moral deterioration as indicated by
the many foul customs, especially as to marriage, of savage tribes. What
does the Jewish tradition of the moral degeneration of man through his
snatching at a knowledge forbidden him by his highest instinct assert
beyond this?") as to lead them regularly to destroy their own offspring, or
to be quite devoid of jealousy. There would have been no prudential
restraint from marriage, and the sexes would have freely united at an early
age. Hence the progenitors of man would have tended to increase rapidly;
but checks of some kind, either periodical or constant, must have kept down
their numbers, even more severely than with existing savages. What the
precise nature of these checks were, we cannot say, any more than with most
other animals. We know that horses and cattle, which are not extremely
prolific animals, when first turned loose in South America, increased at an
enormous rate. The elephant, the slowest breeder of all known animals,
would in a few thousand years stock the whole world. The increase of every
species of monkey must be checked by some means; but not, as Brehm remarks,
by the attacks of beasts of prey. No one will assume that the actual power
of reproduction in the wild horses and cattle of America, was at first in
any sensible degree increased; or that, as each district became fully
stocked, this same power was diminished. No doubt, in this case, and in
all others, many checks concur, and different checks under different
circumstances; periodical dearths, depending on unfavourable seasons, being
probably the most important of all. So it will have been with the early
progenitors of man.
NATURAL SELECTION.
We have now seen that man is variable in body and mind; and that the
variations are induced, either directly or indirectly, by the same general
causes, and obey the same general laws, as with the lower animals. Man has
spread widely over the face of the earth, and must have been exposed,
during his incessant migrations (63. See some good remarks to this effect
by W. Stanley Jevons, "A Deduction from Darwin's Theory," 'Nature,' 1869,
p. 231.), to the most diversified conditions. The inhabitants of Tierra
del Fuego, the Cape of Good Hope, and Tasmania in the one hemisphere, and
of the arctic regions in the other, must have passed through many climates,
and changed their habits many times, before they reached their present
homes. (64. Latham, 'Man and his Migrations,' 1851, p. 135.) The early
progenitors of man must also have tended, like all other animals, to have
increased beyond their means of subsistence; they must, therefore,
occasionally have been exposed to a struggle for existence, and
consequently to the rigid law of natural selection. Beneficial variations
of all kinds will thus, either occasionally or habitually, have been
preserved and injurious ones eliminated. I do not refer to strongly-marked
deviations of structure, which occur only at long intervals of time, but to
mere individual differences. We know, for instance, that the muscles of
our hands and feet, which determine our powers of movement, are liable,
like those of the lower animals, (65. Messrs. Murie and Mivart in their
'Anatomy of the Lemuroidea' ('Transact. Zoolog. Soc.' vol. vii. 1869, pp.
96-98) say, "some muscles are so irregular in their distribution that they
cannot be well classed in any of the above groups." These muscles differ
even on the opposite sides of the same individual.) to incessant
variability. If then the progenitors of man inhabiting any district,
especially one undergoing some change in its conditions, were divided into
two equal bodies, the one half which included all the individuals best
adapted by their powers of movement for gaining subsistence, or for
defending themselves, would on an average survive in greater numbers, and
procreate more offspring than the other and less well endowed half.
Man in the rudest state in which he now exists is the most dominant animal
that has ever appeared on this earth. He has spread more widely than any
other highly organised form: and all others have yielded before him. He
manifestly owes this immense superiority to his intellectual faculties, to
his social habits, which lead him to aid and defend his fellows, and to his
corporeal structure. The supreme importance of these characters has been
proved by the final arbitrament of the battle for life. Through his powers
of intellect, articulate language has been evolved; and on this his
wonderful advancement has mainly depended. As Mr. Chauncey Wright remarks
(66. Limits of Natural Selection, 'North American Review,' Oct. 1870, p.
295.): "a psychological analysis of the faculty of language shews, that
even the smallest proficiency in it might require more brain power than the
greatest proficiency in any other direction." He has invented and is able
to use various weapons, tools, traps, etc., with which he defends himself,
kills or catches prey, and otherwise obtains food. He has made rafts or
canoes for fishing or crossing over to neighbouring fertile islands. He
has discovered the art of making fire, by which hard and stringy roots can
be rendered digestible, and poisonous roots or herbs innocuous. This
discovery of fire, probably the greatest ever made by man, excepting
language, dates from before the dawn of history. These several inventions,
by which man in the rudest state has become so pre-eminent, are the direct
results of the development of his powers of observation, memory, curiosity,
imagination, and reason. I cannot, therefore, understand how it is that
Mr. Wallace (67. 'Quarterly Review,' April 1869, p. 392. This subject is
more fully discussed in Mr. Wallace's 'Contributions to the Theory of
Natural Selection,' 1870, in which all the essays referred to in this work
are re-published. The 'Essay on Man,' has been ably criticised by Prof.
Claparede, one of the most distinguished zoologists in Europe, in an
article published in the 'Bibliotheque Universelle,' June 1870. The remark
quoted in my text will surprise every one who has read Mr. Wallace's
celebrated paper on 'The Origin of Human Races Deduced from the Theory of
Natural Selection,' originally published in the 'Anthropological Review,'
May 1864, p. clviii. I cannot here resist quoting a most just remark by
Sir J. Lubbock ('Prehistoric Times,' 1865, p. 479) in reference to this
paper, namely, that Mr. Wallace, "with characteristic unselfishness,
ascribes it (i.e. the idea of natural selection) unreservedly to Mr.
Darwin, although, as is well known, he struck out the idea independently,
and published it, though not with the same elaboration, at the same time.")
maintains, that "natural selection could only have endowed the savage with
a brain a little superior to that of an ape."
Although the intellectual powers and social habits of man are of paramount
importance to him, we must not underrate the importance of his bodily
structure, to which subject the remainder of this chapter will be devoted;
the development of the intellectual and social or moral faculties being
discussed in a later chapter.
Even to hammer with precision is no easy matter, as every one who has tried
to learn carpentry will admit. To throw a stone with as true an aim as a
Fuegian in defending himself, or in killing birds, requires the most
consummate perfection in the correlated action of the muscles of the hand,
arm, and shoulder, and, further, a fine sense of touch. In throwing a
stone or spear, and in many other actions, a man must stand firmly on his
feet; and this again demands the perfect co-adaptation of numerous muscles.
To chip a flint into the rudest tool, or to form a barbed spear or hook
from a bone, demands the use of a perfect hand; for, as a most capable
judge, Mr. Schoolcraft (68. Quoted by Mr. Lawson Tait in his 'Law of
Natural Selection,' 'Dublin Quarterly Journal of Medical Science,' Feb.
1869. Dr. Keller is likewise quoted to the same effect.), remarks, the
shaping fragments of stone into knives, lances, or arrow-heads, shews
"extraordinary ability and long practice." This is to a great extent
proved by the fact that primeval men practised a division of labour; each
man did not manufacture his own flint tools or rude pottery, but certain
individuals appear to have devoted themselves to such work, no doubt
receiving in exchange the produce of the chase. Archaeologists are
convinced that an enormous interval of time elapsed before our ancestors
thought of grinding chipped flints into smooth tools. One can hardly
doubt, that a man-like animal who possessed a hand and arm sufficiently
perfect to throw a stone with precision, or to form a flint into a rude
tool, could, with sufficient practice, as far as mechanical skill alone is
concerned, make almost anything which a civilised man can make. The
structure of the hand in this respect may be compared with that of the
vocal organs, which in the apes are used for uttering various signal-cries,
or, as in one genus, musical cadences; but in man the closely similar vocal
organs have become adapted through the inherited effects of use for the
utterance of articulate language.
Turning now to the nearest allies of men, and therefore to the best
representatives of our early progenitors, we find that the hands of the
Quadrumana are constructed on the same general pattern as our own, but are
far less perfectly adapted for diversified uses. Their hands do not serve
for locomotion so well as the feet of a dog; as may be seen in such monkeys
as the chimpanzee and orang, which walk on the outer margins of the palms,
or on the knuckles. (69. Owen, 'Anatomy of Vertebrates,' vol. iii. p.
71.) Their hands, however, are admirably adapted for climbing trees.
Monkeys seize thin branches or ropes, with the thumb on one side and the
fingers and palm on the other, in the same manner as we do. They can thus
also lift rather large objects, such as the neck of a bottle, to their
mouths. Baboons turn over stones, and scratch up roots with their hands.
They seize nuts, insects, or other small objects with the thumb in
opposition to the fingers, and no doubt they thus extract eggs and young
from the nests of birds. American monkeys beat the wild oranges on the
branches until the rind is cracked, and then tear it off with the fingers
of the two hands. In a wild state they break open hard fruits with stones.
Other monkeys open mussel-shells with the two thumbs. With their fingers
they pull out thorns and burs, and hunt for each other's parasites. They
roll down stones, or throw them at their enemies: nevertheless, they are
clumsy in these various actions, and, as I have myself seen, are quite
unable to throw a stone with precision.
It seems to me far from true that because "objects are grasped clumsily" by
monkeys, "a much less specialised organ of prehension" would have served
them (70. 'Quarterly Review,' April 1869, p. 392.) equally well with their
present hands. On the contrary, I see no reason to doubt that more
perfectly constructed hands would have been an advantage to them, provided
that they were not thus rendered less fitted for climbing trees. We may
suspect that a hand as perfect as that of man would have been
disadvantageous for climbing; for the most arboreal monkeys in the world,
namely, Ateles in America, Colobus in Africa, and Hylobates in Asia, are
either thumbless, or their toes partially cohere, so that their limbs are
converted into mere grasping hooks. (71. In Hylobates syndactylus, as the
name expresses, two of the toes regularly cohere; and this, as Mr. Blyth
informs me, is occasionally the case with the toes of H. agilis, lar, and
leuciscus. Colobus is strictly arboreal and extraordinarily active (Brehm,
'Thierleben,' B. i. s. 50), but whether a better climber than the species
of the allied genera, I do not know. It deserves notice that the feet of
the sloths, the most arboreal animals in the world, are wonderfully hook-
like.
As soon as some ancient member in the great series of the Primates came to
be less arboreal, owing to a change in its manner of procuring subsistence,
or to some change in the surrounding conditions, its habitual manner of
progression would have been modified: and thus it would have been rendered
more strictly quadrupedal or bipedal. Baboons frequent hilly and rocky
districts, and only from necessity climb high trees (72. Brehm,
'Thierleben,' B. i. s. 80.); and they have acquired almost the gait of a
dog. Man alone has become a biped; and we can, I think, partly see how he
has come to assume his erect attitude, which forms one of his most
conspicuous characters. Man could not have attained his present dominant
position in the world without the use of his hands, which are so admirably
adapted to act in obedience to his will. Sir C. Bell (73. 'The Hand,'
etc., 'Bridgewater Treatise,' 1833, p. 38.) insists that "the hand supplies
all instruments, and by its correspondence with the intellect gives him
universal dominion." But the hands and arms could hardly have become
perfect enough to have manufactured weapons, or to have hurled stones and
spears with a true aim, as long as they were habitually used for locomotion
and for supporting the whole weight of the body, or, as before remarked, so
long as they were especially fitted for climbing trees. Such rough
treatment would also have blunted the sense of touch, on which their
delicate use largely depends. From these causes alone it would have been
an advantage to man to become a biped; but for many actions it is
indispensable that the arms and whole upper part of the body should be
free; and he must for this end stand firmly on his feet. To gain this
great advantage, the feet have been rendered flat; and the great toe has
been peculiarly modified, though this has entailed the almost complete loss
of its power of prehension. It accords with the principle of the division
of physiological labour, prevailing throughout the animal kingdom, that as
the hands became perfected for prehension, the feet should have become
perfected for support and locomotion. With some savages, however, the foot
has not altogether lost its prehensile power, as shewn by their manner of
climbing trees, and of using them in other ways. (74. Haeckel has an
excellent discussion on the steps by which man became a biped: 'Naturliche
Schopfungsgeschicte,' 1868, s. 507. Dr. Buchner ('Conferences sur la
Theorie Darwinienne,' 1869, p. 135) has given good cases of the use of the
foot as a prehensile organ by man; and has also written on the manner of
progression of the higher apes, to which I allude in the following
paragraph: see also Owen ('Anatomy of Vertebrates,' vol. iii. p. 71) on
this latter subject.
If it be an advantage to man to stand firmly on his feet and to have his
hands and arms free, of which, from his pre-eminent success in the battle
of life there can be no doubt, then I can see no reason why it should not
have been advantageous to the progenitors of man to have become more and
more erect or bipedal. They would thus have been better able to defend
themselves with stones or clubs, to attack their prey, or otherwise to
obtain food. The best built individuals would in the long run have
succeeded best, and have survived in larger numbers. If the gorilla and a
few allied forms had become extinct, it might have been argued, with great
force and apparent truth, that an animal could not have been gradually
converted from a quadruped into a biped, as all the individuals in an
intermediate condition would have been miserably ill-fitted for
progression. But we know (and this is well worthy of reflection) that the
anthropomorphous apes are now actually in an intermediate condition; and no
one doubts that they are on the whole well adapted for their conditions of
life. Thus the gorilla runs with a sidelong shambling gait, but more
commonly progresses by resting on its bent hands. The long-armed apes
occasionally use their arms like crutches, swinging their bodies forward
between them, and some kinds of Hylobates, without having been taught, can
walk or run upright with tolerable quickness; yet they move awkwardly, and
much less securely than man. We see, in short, in existing monkeys a
manner of progression intermediate between that of a quadruped and a biped;
but, as an unprejudiced judge (75. Prof. Broca, La Constitution des
Vertebres caudales; 'La Revue d'Anthropologie,' 1872, p. 26, (separate
copy).) insists, the anthropomorphous apes approach in structure more
nearly to the bipedal than to the quadrupedal type.
As the progenitors of man became more and more erect, with their hands and
arms more and more modified for prehension and other purposes, with their
feet and legs at the same time transformed for firm support and
progression, endless other changes of structure would have become
necessary. The pelvis would have to be broadened, the spine peculiarly
curved, and the head fixed in an altered position, all which changes have
been attained by man. Prof. Schaaffhausen (76. 'On the Primitive Form of
the Skull,' translated in 'Anthropological Review,' Oct. 1868, p. 428.
Owen ('Anatomy of Vertebrates,' vol. ii. 1866, p. 551) on the mastoid
processes in the higher apes.) maintains that "the powerful mastoid
processes of the human skull are the result of his erect position;" and
these processes are absent in the orang, chimpanzee, etc., and are smaller
in the gorilla than in man. Various other structures, which appear
connected with man's erect position, might here have been added. It is
very difficult to decide how far these correlated modifications are the
result of natural selection, and how far of the inherited effects of the
increased use of certain parts, or of the action of one part on another.
No doubt these means of change often co-operate: thus when certain
muscles, and the crests of bone to which they are attached, become enlarged
by habitual use, this shews that certain actions are habitually performed
and must be serviceable. Hence the individuals which performed them best,
would tend to survive in greater numbers.
The free use of the arms and hands, partly the cause and partly the result
of man's erect position, appears to have led in an indirect manner to other
modifications of structure. The early male forefathers of man were, as
previously stated, probably furnished with great canine teeth; but as they
gradually acquired the habit of using stones, clubs, or other weapons, for
fighting with their enemies or rivals, they would use their jaws and teeth
less and less. In this case, the jaws, together with the teeth, would
become reduced in size, as we may feel almost sure from innumerable
analogous cases. In a future chapter we shall meet with a closely parallel
case, in the reduction or complete disappearance of the canine teeth in
male ruminants, apparently in relation with the development of their horns;
and in horses, in relation to their habit of fighting with their incisor
teeth and hoofs.
In the adult male anthropomorphous apes, as Rutimeyer (77. 'Die Grenzen
der Thierwelt, eine Betrachtung zu Darwin's Lehre,' 1868, s. 51.), and
others, have insisted, it is the effect on the skull of the great
development of the jaw-muscles that causes it to differ so greatly in many
respects from that of man, and has given to these animals "a truly
frightful physiognomy." Therefore, as the jaws and teeth in man's
progenitors gradually become reduced in size, the adult skull would have
come to resemble more and more that of existing man. As we shall hereafter
see, a great reduction of the canine teeth in the males would almost
certainly affect the teeth of the females through inheritance.
As the various mental faculties gradually developed themselves the brain
would almost certainly become larger. No one, I presume, doubts that the
large proportion which the size of man's brain bears to his body, compared
to the same proportion in the gorilla or orang, is closely connected with
his higher mental powers. We meet with closely analogous facts with
insects, for in ants the cerebral ganglia are of extraordinary dimensions,
and in all the Hymenoptera these ganglia are many times larger than in the
less intelligent orders, such as beetles. (78. Dujardin, 'Annales des
Sciences Nat.' 3rd series, Zoolog., tom. xiv. 1850, p. 203. See also Mr.
Lowne, 'Anatomy and Phys. of the Musca vomitoria,' 1870, p. 14. My son,
Mr. F. Darwin, dissected for me the cerebral ganglia of the Formica rufa.)
On the other hand, no one supposes that the intellect of any two animals or
of any two men can be accurately gauged by the cubic contents of their
skulls. It is certain that there may be extraordinary mental activity with
an extremely small absolute mass of nervous matter: thus the wonderfully
diversified instincts, mental powers, and affections of ants are notorious,
yet their cerebral ganglia are not so large as the quarter of a small pin's
head. Under this point of view, the brain of an ant is one of the most
marvellous atoms of matter in the world, perhaps more so than the brain of
a man.
The belief that there exists in man some close relation between the size of
the brain and the development of the intellectual faculties is supported by
the comparison of the skulls of savage and civilised races, of ancient and
modern people, and by the analogy of the whole vertebrate series. Dr. J.
Barnard Davis has proved (79. 'Philosophical Transactions,' 1869, p.
513.), by many careful measurements, that the mean internal capacity of the
skull in Europeans is 92.3 cubic inches; in Americans 87.5; in Asiatics
87.1; and in Australians only 81.9 cubic inches. Professor Broca (80.
'Les Selections,' M. P. Broca, 'Revue d'Anthropologies,' 1873; see also, as
quoted in C. Vogt's 'Lectures on Man,' Engl. translat., 1864, pp. 88, 90.
Prichard, 'Physical History of Mankind,' vol. i. 1838, p. 305.) found that
the nineteenth century skulls from graves in Paris were larger than those
from vaults of the twelfth century, in the proportion of 1484 to 1426; and
that the increased size, as ascertained by measurements, was exclusively in
the frontal part of the skull--the seat of the intellectual faculties.
Prichard is persuaded that the present inhabitants of Britain have "much
more capacious brain-cases" than the ancient inhabitants. Nevertheless, it
must be admitted that some skulls of very high antiquity, such as the
famous one of Neanderthal, are well developed and capacious. (81. In the
interesting article just referred to, Prof. Broca has well remarked, that
in civilised nations, the average capacity of the skull must be lowered by
the preservation of a considerable number of individuals, weak in mind and
body, who would have been promptly eliminated in the savage state. On the
other hand, with savages, the average includes only the more capable
individuals, who have been able to survive under extremely hard conditions
of life. Broca thus explains the otherwise inexplicable fact, that the
mean capacity of the skull of the ancient Troglodytes of Lozere is greater
than that of modern Frenchmen.) With respect to the lower animals, M.E.
Lartet (82. 'Comptes-rendus des Sciences,' etc., June 1, 1868.), by
comparing the crania of tertiary and recent mammals belonging to the same
groups, has come to the remarkable conclusion that the brain is generally
larger and the convolutions are more complex in the more recent forms. On
the other hand, I have shewn (83. The 'Variation of Animals and Plants
under Domestication,' vol. i. pp. 124-129.) that the brains of domestic
rabbits are considerably reduced in bulk, in comparison with those of the
wild rabbit or hare; and this may be attributed to their having been
closely confined during many generations, so that they have exerted their
intellect, instincts, senses and voluntary movements but little.
The gradually increasing weight of the brain and skull in man must have
influenced the development of the supporting spinal column, more especially
whilst he was becoming erect. As this change of position was being brought
about, the internal pressure of the brain will also have influenced the
form of the skull; for many facts shew how easily the skull is thus
affected. Ethnologists believe that it is modified by the kind of cradle
in which infants sleep. Habitual spasms of the muscles, and a cicatrix
from a severe burn, have permanently modified the facial bones. In young
persons whose heads have become fixed either sideways or backwards, owing
to disease, one of the two eyes has changed its position, and the shape of
the skull has been altered apparently by the pressure of the brain in a new
direction. (84. Schaaffhausen gives from Blumenbach and Busch, the cases
of the spasms and cicatrix, in 'Anthropological Review,' Oct. 1868, p. 420.
Dr. Jarrold ('Anthropologia,' 1808, pp. 115, 116) adduces from Camper and
from his own observations, cases of the modification of the skull from the
head being fixed in an unnatural position. He believes that in certain
trades, such as that of a shoemaker, where the head is habitually held
forward, the forehead becomes more rounded and prominent.) I have shewn
that with long-eared rabbits even so trifling a cause as the lopping
forward of one ear drags forward almost every bone of the skull on that
side; so that the bones on the opposite side no longer strictly correspond.
Lastly, if any animal were to increase or diminish much in general size,
without any change in its mental powers, or if the mental powers were to be
much increased or diminished, without any great change in the size of the
body, the shape of the skull would almost certainly be altered. I infer
this from my observations on domestic rabbits, some kinds of which have
become very much larger than the wild animal, whilst others have retained
nearly the same size, but in both cases the brain has been much reduced
relatively to the size of the body. Now I was at first much surprised on
finding that in all these rabbits the skull had become elongated or
dolichocephalic; for instance, of two skulls of nearly equal breadth, the
one from a wild rabbit and the other from a large domestic kind, the former
was 3.15 and the latter 4.3 inches in length. (85. 'Variation of Animals
and Plants under Domestication,' vol. i. p. 117, on the elongation of the
skull; p. 119, on the effect of the lopping of one ear.) One of the most
marked distinctions in different races of men is that the skull in some is
elongated, and in others rounded; and here the explanation suggested by the
case of the rabbits may hold good; for Welcker finds that short "men
incline more to brachycephaly, and tall men to dolichocephaly" (86. Quoted
by Schaaffhausen, in 'Anthropological Review,' Oct. 1868, p. 419.); and
tall men may be compared with the larger and longer-bodied rabbits, all of
which have elongated skulls or are dolichocephalic.
From these several facts we can understand, to a certain extent, the means
by which the great size and more or less rounded form of the skull have
been acquired by man; and these are characters eminently distinctive of him
in comparison with the lower animals.
Another most conspicuous difference between man and the lower animals is
the nakedness of his skin. Whales and porpoises (Cetacea), dugongs
(Sirenia) and the hippopotamus are naked; and this may be advantageous to
them for gliding through the water; nor would it be injurious to them from
the loss of warmth, as the species, which inhabit the colder regions, are
protected by a thick layer of blubber, serving the same purpose as the fur
of seals and otters. Elephants and rhinoceroses are almost hairless; and
as certain extinct species, which formerly lived under an Arctic climate,
were covered with long wool or hair, it would almost appear as if the
existing species of both genera had lost their hairy covering from exposure
to heat. This appears the more probable, as the elephants in India which
live on elevated and cool districts are more hairy (87. Owen, 'Anatomy of
Vertebrates,' vol. iii. p. 619.) than those on the lowlands. May we then
infer that man became divested of hair from having aboriginally inhabited
some tropical land? That the hair is chiefly retained in the male sex on
the chest and face, and in both sexes at the junction of all four limbs
with the trunk, favours this inference--on the assumption that the hair was
lost before man became erect; for the parts which now retain most hair
would then have been most protected from the heat of the sun. The crown of
the head, however, offers a curious exception, for at all times it must
have been one of the most exposed parts, yet it is thickly clothed with
hair. The fact, however, that the other members of the order of Primates,
to which man belongs, although inhabiting various hot regions, are well
clothed with hair, generally thickest on the upper surface (88. Isidore
Geoffroy St.-Hilaire remarks ('Histoire Nat. Generale,' tom. ii. 1859, pp.
215-217) on the head of man being covered with long hair; also on the upper
surfaces of monkeys and of other mammals being more thickly clothed than
the lower surfaces. This has likewise been observed by various authors.
Prof. P. Gervais ('Histoire Nat. des Mammiferes,' tom. i. 1854, p. 28),
however, states that in the Gorilla the hair is thinner on the back, where
it is partly rubbed off, than on the lower surface.), is opposed to the
supposition that man became naked through the action of the sun. Mr. Belt
believes (89. The 'Naturalist in Nicaragua,' 1874, p. 209. As some
confirmation of Mr. Belt's view, I may quote the following passage from Sir
W. Denison ('Varieties of Vice-Regal Life,' vol. i. 1870, p. 440): "It is
said to be a practice with the Australians, when the vermin get
troublesome, to singe themselves.") that within the tropics it is an
advantage to man to be destitute of hair, as he is thus enabled to free
himself of the multitude of ticks (acari) and other parasites, with which
he is often infested, and which sometimes cause ulceration. But whether
this evil is of sufficient magnitude to have led to the denudation of his
body through natural selection, may be doubted, since none of the many
quadrupeds inhabiting the tropics have, as far as I know, acquired any
specialised means of relief. The view which seems to me the most probable
is that man, or rather primarily woman, became divested of hair for
ornamental purposes, as we shall see under Sexual Selection; and, according
to this belief, it is not surprising that man should differ so greatly in
hairiness from all other Primates, for characters, gained through sexual
selection, often differ to an extraordinary degree in closely related
forms.
According to a popular impression, the absence of a tail is eminently
distinctive of man; but as those apes which come nearest to him are
destitute of this organ, its disappearance does not relate exclusively to
man. The tail often differs remarkably in length within the same genus:
thus in some species of Macacus it is longer than the whole body, and is
formed of twenty-four vertebrae; in others it consists of a scarcely
visible stump, containing only three or four vertebrae. In some kinds of
baboons there are twenty-five, whilst in the mandrill there are ten very
small stunted caudal vertebrae, or, according to Cuvier (90. Mr. St.
George Mivart, 'Proc. Zoolog. Soc.' 1865, pp. 562, 583. Dr. J.E. Gray,
'Cat. Brit. Mus.: 'Skeletons.' Owen, 'Anatomy of Vertebrates,' vol. ii.
p. 517. Isidore Geoffroy, 'Hist. Nat. Gen.' tom. ii. p. 244.), sometimes
only five. The tail, whether it be long or short, almost always tapers
towards the end; and this, I presume, results from the atrophy of the
terminal muscles, together with their arteries and nerves, through disuse,
leading to the atrophy of the terminal bones. But no explanation can at
present be given of the great diversity which often occurs in its length.
Here, however, we are more specially concerned with the complete external
disappearance of the tail. Professor Broca has recently shewn (91. 'Revue
d'Anthropologie,' 1872; 'La Constitution des vertebres caudales.') that the
tail in all quadrupeds consists of two portions, generally separated
abruptly from each other; the basal portion consists of vertebrae, more or
less perfectly channelled and furnished with apophyses like ordinary
vertebrae; whereas those of the terminal portion are not channelled, are
almost smooth, and scarcely resemble true vertebrae. A tail, though not
externally visible, is really present in man and the anthropomorphous apes,
and is constructed on exactly the same pattern in both. In the terminal
portion the vertabrae, constituting the os coccyx, are quite rudimentary,
being much reduced in size and number. In the basal portion, the vertebrae
are likewise few, are united firmly together, and are arrested in
development; but they have been rendered much broader and flatter than the
corresponding vertebrae in the tails of other animals: they constitute
what Broca calls the accessory sacral vertebrae. These are of functional
importance by supporting certain internal parts and in other ways; and
their modification is directly connected with the erect or semi-erect
attitude of man and the anthropomorphous apes. This conclusion is the more
trustworthy, as Broca formerly held a different view, which he has now
abandoned. The modification, therefore, of the basal caudal vertebrae in
man and the higher apes may have been effected, directly or indirectly,
through natural selection.
But what are we to say about the rudimentary and variable vertebrae of the
terminal portion of the tail, forming the os coccyx? A notion which has
often been, and will no doubt again be ridiculed, namely, that friction has
had something to do with the disappearance of the external portion of the
tail, is not so ridiculous as it at first appears. Dr. Anderson (92.
'Proceedings Zoological Society,' 1872, p. 210.) states that the extremely
short tail of Macacus brunneus is formed of eleven vertebrae, including the
imbedded basal ones. The extremity is tendinous and contains no vertebrae;
this is succeeded by five rudimentary ones, so minute that together they
are only one line and a half in length, and these are permanently bent to
one side in the shape of a hook. The free part of the tail, only a little
above an inch in length, includes only four more small vertebrae. This
short tail is carried erect; but about a quarter of its total length is
doubled on to itself to the left; and this terminal part, which includes
the hook-like portion, serves "to fill up the interspace between the upper
divergent portion of the callosities;" so that the animal sits on it, and
thus renders it rough and callous. Dr. Anderson thus sums up his
observations: "These facts seem to me to have only one explanation; this
tail, from its short size, is in the monkey's way when it sits down, and
frequently becomes placed under the animal while it is in this attitude;
and from the circumstance that it does not extend beyond the extremity of
the ischial tuberosities, it seems as if the tail originally had been bent
round by the will of the animal, into the interspace between the
callosities, to escape being pressed between them and the ground, and that
in time the curvature became permanent, fitting in of itself when the organ
happens to be sat upon." Under these circumstances it is not surprising
that the surface of the tail should have been roughened and rendered
callous, and Dr. Murie (93. 'Proceedings Zoological Society,' 1872, p.
786.), who carefully observed this species in the Zoological Gardens, as
well as three other closely allied forms with slightly longer tails, says
that when the animal sits down, the tail "is necessarily thrust to one side
of the buttocks; and whether long or short its root is consequently liable
to be rubbed or chafed." As we now have evidence that mutilations
occasionally produce an inherited effect (94. I allude to Dr. Brown-
Sequard's observations on the transmitted effect of an operation causing
epilepsy in guinea-pigs, and likewise more recently on the analogous
effects of cutting the sympathetic nerve in the neck. I shall hereafter
have occasion to refer to Mr. Salvin's interesting case of the apparently
inherited effects of mot-mots biting off the barbs of their own tail-
feathers. See also on the general subject 'Variation of Animals and Plants
under Domestication,' vol. ii. pp. 22-24.), it is not very improbable that
in short-tailed monkeys, the projecting part of the tail, being
functionally useless, should after many generations have become rudimentary
and distorted, from being continually rubbed and chafed. We see the
projecting part in this condition in the Macacus brunneus, and absolutely
aborted in the M. ecaudatus and in several of the higher apes. Finally,
then, as far as we can judge, the tail has disappeared in man and the
anthropomorphous apes, owing to the terminal portion having been injured by
friction during a long lapse of time; the basal and embedded portion having
been reduced and modified, so as to become suitable to the erect or semi-
erect position.
I have now endeavoured to shew that some of the most distinctive characters
of man have in all probability been acquired, either directly, or more
commonly indirectly, through natural selection. We should bear in mind
that modifications in structure or constitution which do not serve to adapt
an organism to its habits of life, to the food which it consumes, or
passively to the surrounding conditions, cannot have been thus acquired.
We must not, however, be too confident in deciding what modifications are
of service to each being: we should remember how little we know about the
use of many parts, or what changes in the blood or tissues may serve to fit
an organism for a new climate or new kinds of food. Nor must we forget the
principle of correlation, by which, as Isidore Geoffroy has shewn in the
case of man, many strange deviations of structure are tied together.
Independently of correlation, a change in one part often leads, through the
increased or decreased use of other parts, to other changes of a quite
unexpected nature. It is also well to reflect on such facts, as the
wonderful growth of galls on plants caused by the poison of an insect, and
on the remarkable changes of colour in the plumage of parrots when fed on
certain fishes, or inoculated with the poison of toads (95. The 'Variation
of Animals and Plants under Domestication,' vol. ii. pp. 280, 282.); for we
can thus see that the fluids of the system, if altered for some special
purpose, might induce other changes. We should especially bear in mind
that modifications acquired and continually used during past ages for some
useful purpose, would probably become firmly fixed, and might be long
inherited.
Thus a large yet undefined extension may safely be given to the direct and
indirect results of natural selection; but I now admit, after reading the
essay by Nageli on plants, and the remarks by various authors with respect
to animals, more especially those recently made by Professor Broca, that in
the earlier editions of my 'Origin of Species' I perhaps attributed too
much to the action of natural selection or the survival of the fittest. I
have altered the fifth edition of the 'Origin' so as to confine my remarks
to adaptive changes of structure; but I am convinced, from the light gained
during even the last few years, that very many structures which now appear
to us useless, will hereafter be proved to be useful, and will therefore
come within the range of natural selection. Nevertheless, I did not
formerly consider sufficiently the existence of structures, which, as far
as we can at present judge, are neither beneficial nor injurious; and this
I believe to be one of the greatest oversights as yet detected in my work.
I may be permitted to say, as some excuse, that I had two distinct objects
in view; firstly, to shew that species had not been separately created, and
secondly, that natural selection had been the chief agent of change, though
largely aided by the inherited effects of habit, and slightly by the direct
action of the surrounding conditions. I was not, however, able to annul
the influence of my former belief, then almost universal, that each species
had been purposely created; and this led to my tacit assumption that every
detail of structure, excepting rudiments, was of some special, though
unrecognised, service. Any one with this assumption in his mind would
naturally extend too far the action of natural selection, either during
past or present times. Some of those who admit the principle of evolution,
but reject natural selection, seem to forget, when criticising my book,
that I had the above two objects in view; hence if I have erred in giving
to natural selection great power, which I am very far from admitting, or in
having exaggerated its power, which is in itself probable, I have at least,
as I hope, done good service in aiding to overthrow the dogma of separate
creations.
It is, as I can now see, probable that all organic beings, including man,
possess peculiarities of structure, which neither are now, nor were
formerly of any service to them, and which, therefore, are of no
physiological importance. We know not what produces the numberless slight
differences between the individuals of each species, for reversion only
carries the problem a few steps backwards, but each peculiarity must have
had its efficient cause. If these causes, whatever they may be, were to
act more uniformly and energetically during a lengthened period (and
against this no reason can be assigned), the result would probably be not a
mere slight individual difference, but a well-marked and constant
modification, though one of no physiological importance. Changed
structures, which are in no way beneficial, cannot be kept uniform through
natural selection, though the injurious will be thus eliminated.
Uniformity of character would, however, naturally follow from the assumed
uniformity of the exciting causes, and likewise from the free intercrossing
of many individuals. During successive periods, the same organism might in
this manner acquire successive modifications, which would be transmitted in
a nearly uniform state as long as the exciting causes remained the same and
there was free intercrossing. With respect to the exciting causes we can
only say, as when speaking of so-called spontaneous variations, that they
relate much more closely to the constitution of the varying organism, than
to the nature of the conditions to which it has been subjected.
CONCLUSION.
In this chapter we have seen that as man at the present day is liable, like
every other animal, to multiform individual differences or slight
variations, so no doubt were the early progenitors of man; the variations
being formerly induced by the same general causes, and governed by the same
general and complex laws as at present. As all animals tend to multiply
beyond their means of subsistence, so it must have been with the
progenitors of man; and this would inevitably lead to a struggle for
existence and to natural selection. The latter process would be greatly
aided by the inherited effects of the increased use of parts, and these two
processes would incessantly react on each other. It appears, also, as we
shall hereafter see, that various unimportant characters have been acquired
by man through sexual selection. An unexplained residuum of change must be
left to the assumed uniform action of those unknown agencies, which
occasionally induce strongly marked and abrupt deviations of structure in
our domestic productions.
Judging from the habits of savages and of the greater number of the
Quadrumana, primeval men, and even their ape-like progenitors, probably
lived in society. With strictly social animals, natural selection
sometimes acts on the individual, through the preservation of variations
which are beneficial to the community. A community which includes a large
number of well-endowed individuals increases in number, and is victorious
over other less favoured ones; even although each separate member gains no
advantage over the others of the same community. Associated insects have
thus acquired many remarkable structures, which are of little or no service
to the individual, such as the pollen-collecting apparatus, or the sting of
the worker-bee, or the great jaws of soldier-ants. With the higher social
animals, I am not aware that any structure has been modified solely for the
good of the community, though some are of secondary service to it. For
instance, the horns of ruminants and the great canine teeth of baboons
appear to have been acquired by the males as weapons for sexual strife, but
they are used in defence of the herd or troop. In regard to certain mental
powers the case, as we shall see in the fifth chapter, is wholly different;
for these faculties have been chiefly, or even exclusively, gained for the
benefit of the community, and the individuals thereof have at the same time
gained an advantage indirectly.
It has often been objected to such views as the foregoing, that man is one
of the most helpless and defenceless creatures in the world; and that
during his early and less well-developed condition, he would have been
still more helpless. The Duke of Argyll, for instance, insists (96.
'Primeval Man,' 1869, p. 66.) that "the human frame has diverged from the
structure of brutes, in the direction of greater physical helplessness and
weakness. That is to say, it is a divergence which of all others it is
most impossible to ascribe to mere natural selection." He adduces the
naked and unprotected state of the body, the absence of great teeth or
claws for defence, the small strength and speed of man, and his slight
power of discovering food or of avoiding danger by smell. To these
deficiencies there might be added one still more serious, namely, that he
cannot climb quickly, and so escape from enemies. The loss of hair would
not have been a great injury to the inhabitants of a warm country. For we
know that the unclothed Fuegians can exist under a wretched climate. When
we compare the defenceless state of man with that of apes, we must remember
that the great canine teeth with which the latter are provided, are
possessed in their full development by the males alone, and are chiefly
used by them for fighting with their rivals; yet the females, which are not
thus provided, manage to survive.
In regard to bodily size or strength, we do not know whether man is
descended from some small species, like the chimpanzee, or from one as
powerful as the gorilla; and, therefore, we cannot say whether man has
become larger and stronger, or smaller and weaker, than his ancestors. We
should, however, bear in mind that an animal possessing great size,
strength, and ferocity, and which, like the gorilla, could defend itself
from all enemies, would not perhaps have become social: and this would
most effectually have checked the acquirement of the higher mental
qualities, such as sympathy and the love of his fellows. Hence it might
have been an immense advantage to man to have sprung from some
comparatively weak creature.
The small strength and speed of man, his want of natural weapons, etc., are
more than counterbalanced, firstly, by his intellectual powers, through
which he has formed for himself weapons, tools, etc., though still
remaining in a barbarous state, and, secondly, by his social qualities
which lead him to give and receive aid from his fellow-men. No country in
the world abounds in a greater degree with dangerous beasts than Southern
Africa; no country presents more fearful physical hardships than the Arctic
regions; yet one of the puniest of races, that of the Bushmen, maintains
itself in Southern Africa, as do the dwarfed Esquimaux in the Arctic
regions. The ancestors of man were, no doubt, inferior in intellect, and
probably in social disposition, to the lowest existing savages; but it is
quite conceivable that they might have existed, or even flourished, if
they had advanced in intellect, whilst gradually losing their brute-like
powers, such as that of climbing trees, etc. But these ancestors would not
have been exposed to any special danger, even if far more helpless and
defenceless than any existing savages, had they inhabited some warm
continent or large island, such as Australia, New Guinea, or Borneo, which
is now the home of the orang. And natural selection arising from the
competition of tribe with tribe, in some such large area as one of these,
together with the inherited effects of habit, would, under favourable
conditions, have sufficed to raise man to his present high position in the
organic scale.
CHAPTER III.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS.
The difference in mental power between the highest ape and the lowest
savage, immense--Certain instincts in common--The emotions--Curiosity--
Imitation--Attention--Memory--Imagination--Reason--Progressive improvement
--Tools and weapons used by animals--Abstraction, Self-consciousness--
Language--Sense of beauty--Belief in God, spiritual agencies,
superstitions.
We have seen in the last two chapters that man bears in his bodily
structure clear traces of his descent from some lower form; but it may be
urged that, as man differs so greatly in his mental power from all other
animals, there must be some error in this conclusion. No doubt the
difference in this respect is enormous, even if we compare the mind of one
of the lowest savages, who has no words to express any number higher than
four, and who uses hardly any abstract terms for common objects or for the
affections (1. See the evidence on those points, as given by Lubbock,
'Prehistoric Times,' p. 354, etc.), with that of the most highly organised
ape. The difference would, no doubt, still remain immense, even if one of
the higher apes had been improved or civilised as much as a dog has been in
comparison with its parent-form, the wolf or jackal. The Fuegians rank
amongst the lowest barbarians; but I was continually struck with surprise
how closely the three natives on board H.M.S. "Beagle," who had lived some
years in England, and could talk a little English, resembled us in
disposition and in most of our mental faculties. If no organic being
excepting man had possessed any mental power, or if his powers had been of
a wholly different nature from those of the lower animals, then we should
never have been able to convince ourselves that our high faculties had been
gradually developed. But it can be shewn that there is no fundamental
difference of this kind. We must also admit that there is a much wider
interval in mental power between one of the lowest fishes, as a lamprey or
lancelet, and one of the higher apes, than between an ape and man; yet this
interval is filled up by numberless gradations.
Nor is the difference slight in moral disposition between a barbarian, such
as the man described by the old navigator Byron, who dashed his child on
the rocks for dropping a basket of sea-urchins, and a Howard or Clarkson;
and in intellect, between a savage who uses hardly any abstract terms, and
a Newton or Shakspeare. Differences of this kind between the highest men
of the highest races and the lowest savages, are connected by the finest
gradations. Therefore it is possible that they might pass and be developed
into each other.
My object in this chapter is to shew that there is no fundamental
difference between man and the higher mammals in their mental faculties.
Each division of the subject might have been extended into a separate
essay, but must here be treated briefly. As no classification of the
mental powers has been universally accepted, I shall arrange my remarks in
the order most convenient for my purpose; and will select those facts which
have struck me most, with the hope that they may produce some effect on the
reader.
With respect to animals very low in the scale, I shall give some additional
facts under Sexual Selection, shewing that their mental powers are much
higher than might have been expected. The variability of the faculties in
the individuals of the same species is an important point for us, and some
few illustrations will here be given. But it would be superfluous to enter
into many details on this head, for I have found on frequent enquiry, that
it is the unanimous opinion of all those who have long attended to animals
of many kinds, including birds, that the individuals differ greatly in
every mental characteristic. In what manner the mental powers were first
developed in the lowest organisms, is as hopeless an enquiry as how life
itself first originated. These are problems for the distant future, if
they are ever to be solved by man.
As man possesses the same senses as the lower animals, his fundamental
intuitions must be the same. Man has also some few instincts in common, as
that of self-preservation, sexual love, the love of the mother for her new-
born offspring, the desire possessed by the latter to suck, and so forth.
But man, perhaps, has somewhat fewer instincts than those possessed by the
animals which come next to him in the series. The orang in the Eastern
islands, and the chimpanzee in Africa, build platforms on which they sleep;
and, as both species follow the same habit, it might be argued that this
was due to instinct, but we cannot feel sure that it is not the result of
both animals having similar wants, and possessing similar powers of
reasoning. These apes, as we may assume, avoid the many poisonous fruits
of the tropics, and man has no such knowledge: but as our domestic
animals, when taken to foreign lands, and when first turned out in the
spring, often eat poisonous herbs, which they afterwards avoid, we cannot
feel sure that the apes do not learn from their own experience or from that
of their parents what fruits to select. It is, however, certain, as we
shall presently see, that apes have an instinctive dread of serpents, and
probably of other dangerous animals.
The fewness and the comparative simplicity of the instincts in the higher
animals are remarkable in contrast with those of the lower animals. Cuvier
maintained that instinct and intelligence stand in an inverse ratio to each
other; and some have thought that the intellectual faculties of the higher
animals have been gradually developed from their instincts. But Pouchet,
in an interesting essay (2. 'L'Instinct chez les Insectes,' 'Revue des
Deux Mondes,' Feb. 1870, p. 690.), has shewn that no such inverse ratio
really exists. Those insects which possess the most wonderful instincts
are certainly the most intelligent. In the vertebrate series, the least
intelligent members, namely fishes and amphibians, do not possess complex
instincts; and amongst mammals the animal most remarkable for its
instincts, namely the beaver, is highly intelligent, as will be admitted by
every one who has read Mr. Morgan's excellent work. (3. 'The American
Beaver and His Works,' 1868.)
Although the first dawnings of intelligence, according to Mr. Herbert
Spencer (4. 'The Principles of Psychology,' 2nd edit., 1870, pp. 418-
443.), have been developed through the multiplication and co-ordination of
reflex actions, and although many of the simpler instincts graduate into
reflex actions, and can hardly be distinguished from them, as in the case
of young animals sucking, yet the more complex instincts seem to have
originated independently of intelligence. I am, however, very far from
wishing to deny that instinctive actions may lose their fixed and untaught
character, and be replaced by others performed by the aid of the free will.
On the other hand, some intelligent actions, after being performed during
several generations, become converted into instincts and are inherited, as
when birds on oceanic islands learn to avoid man. These actions may then
be said to be degraded in character, for they are no longer performed
through reason or from experience. But the greater number of the more
complex instincts appear to have been gained in a wholly different manner,
through the natural selection of variations of simpler instinctive actions.
Such variations appear to arise from the same unknown causes acting on the
cerebral organisation, which induce slight variations or individual
differences in other parts of the body; and these variations, owing to our
ignorance, are often said to arise spontaneously. We can, I think, come to
no other conclusion with respect to the origin of the more complex
instincts, when we reflect on the marvellous instincts of sterile worker-
ants and bees, which leave no offspring to inherit the effects of
experience and of modified habits.
Although, as we learn from the above-mentioned insects and the beaver, a
high degree of intelligence is certainly compatible with complex instincts,
and although actions, at first learnt voluntarily can soon through habit be
performed with the quickness and certainty of a reflex action, yet it is
not improbable that there is a certain amount of interference between the
development of free intelligence and of instinct,--which latter implies
some inherited modification of the brain. Little is known about the
functions of the brain, but we can perceive that as the intellectual powers
become highly developed, the various parts of the brain must be connected
by very intricate channels of the freest intercommunication; and as a
consequence each separate part would perhaps tend to be less well fitted to
answer to particular sensations or associations in a definite and
inherited--that is instinctive--manner. There seems even to exist some
relation between a low degree of intelligence and a strong tendency to the
formation of fixed, though not inherited habits; for as a sagacious
physician remarked to me, persons who are slightly imbecile tend to act in
everything by routine or habit; and they are rendered much happier if this
is encouraged.
I have thought this digression worth giving, because we may easily
underrate the mental powers of the higher animals, and especially of man,
when we compare their actions founded on the memory of past events, on
foresight, reason, and imagination, with exactly similar actions
instinctively performed by the lower animals; in this latter case the
capacity of performing such actions has been gained, step by step, through
the variability of the mental organs and natural selection, without any
conscious intelligence on the part of the animal during each successive
generation. No doubt, as Mr. Wallace has argued (5. 'Contributions to the
Theory of Natural Selection,' 1870, p. 212.), much of the intelligent work
done by man is due to imitation and not to reason; but there is this great
difference between his actions and many of those performed by the lower
animals, namely, that man cannot, on his first trial, make, for instance, a
stone hatchet or a canoe, through his power of imitation. He has to learn
his work by practice; a beaver, on the other hand, can make its dam or
canal, and a bird its nest, as well, or nearly as well, and a spider its
wonderful web, quite as well (6. For the evidence on this head, see Mr. J.
Traherne Moggridge's most interesting work, 'Harvesting Ants and Trap-Door
Spiders,' 1873, pp. 126, 128.), the first time it tries as when old and
experienced.
To return to our immediate subject: the lower animals, like man,
manifestly feel pleasure and pain, happiness and misery. Happiness is
never better exhibited than by young animals, such as puppies, kittens,
lambs, etc., when playing together, like our own children. Even insects
play together, as has been described by that excellent observer, P. Huber
(7. 'Recherches sur les Moeurs des Fourmis,' 1810, p. 173.), who saw ants
chasing and pretending to bite each other, like so many puppies.
The fact that the lower animals are excited by the same emotions as
ourselves is so well established, that it will not be necessary to weary
the reader by many details. Terror acts in the same manner on them as on
us, causing the muscles to tremble, the heart to palpitate, the sphincters
to be relaxed, and the hair to stand on end. Suspicion, the offspring of
fear, is eminently characteristic of most wild animals. It is, I think,
impossible to read the account given by Sir E. Tennent, of the behaviour of
the female elephants, used as decoys, without admitting that they
intentionally practise deceit, and well know what they are about. Courage
and timidity are extremely variable qualities in the individuals of the
same species, as is plainly seen in our dogs. Some dogs and horses are
ill-tempered, and easily turn sulky; others are good-tempered; and these
qualities are certainly inherited. Every one knows how liable animals are
to furious rage, and how plainly they shew it. Many, and probably true,
anecdotes have been published on the long-delayed and artful revenge of
various animals. The accurate Rengger, and Brehm (8. All the following
statements, given on the authority of these two naturalists, are taken from
Rengger's 'Naturgesch. der Saugethiere von Paraguay,' 1830, s. 41-57, and
from Brehm's 'Thierleben,' B. i. s. 10-87.) state that the American and
African monkeys which they kept tame, certainly revenged themselves. Sir
Andrew Smith, a zoologist whose scrupulous accuracy was known to many
persons, told me the following story of which he was himself an eye-
witness; at the Cape of Good Hope an officer had often plagued a certain
baboon, and the animal, seeing him approaching one Sunday for parade,
poured water into a hole and hastily made some thick mud, which he
skilfully dashed over the officer as he passed by, to the amusement of many
bystanders. For long afterwards the baboon rejoiced and triumphed whenever
he saw his victim.
The love of a dog for his master is notorious; as an old writer quaintly
says (9. Quoted by Dr. Lauder Lindsay, in his 'Physiology of Mind in the
Lower Animals,' 'Journal of Mental Science,' April 1871, p. 38.), "A dog is
the only thing on this earth that luvs you more than he luvs himself."
In the agony of death a dog has been known to caress his master, and every
one has heard of the dog suffering under vivisection, who licked the hand
of the operator; this man, unless the operation was fully justified by an
increase of our knowledge, or unless he had a heart of stone, must have
felt remorse to the last hour of his life.
As Whewell (10. 'Bridgewater Treatise,' p. 263.) has well asked, "who that
reads the touching instances of maternal affection, related so often of the
women of all nations, and of the females of all animals, can doubt that the
principle of action is the same in the two cases?" We see maternal
affection exhibited in the most trifling details; thus Rengger observed an
American monkey (a Cebus) carefully driving away the flies which plagued
her infant; and Duvaucel saw a Hylobates washing the faces of her young
ones in a stream. So intense is the grief of female monkeys for the loss
of their young, that it invariably caused the death of certain kinds kept
under confinement by Brehm in N. Africa. Orphan monkeys were always
adopted and carefully guarded by the other monkeys, both males and females.
One female baboon had so capacious a heart that she not only adopted young
monkeys of other species, but stole young dogs and cats, which she
continually carried about. Her kindness, however, did not go so far as to
share her food with her adopted offspring, at which Brehm was surprised, as
his monkeys always divided everything quite fairly with their own young
ones. An adopted kitten scratched this affectionate baboon, who certainly
had a fine intellect, for she was much astonished at being scratched, and
immediately examined the kitten's feet, and without more ado bit off the
claws. (11. A critic, without any grounds ('Quarterly Review,' July 1871,
p. 72), disputes the possibility of this act as described by Brehm, for the
sake of discrediting my work. Therefore I tried, and found that I could
readily seize with my own teeth the sharp little claws of a kitten nearly
five weeks old.) In the Zoological Gardens, I heard from the keeper that
an old baboon (C. chacma) had adopted a Rhesus monkey; but when a young
drill and mandrill were placed in the cage, she seemed to perceive that
these monkeys, though distinct species, were her nearer relatives, for she
at once rejected the Rhesus and adopted both of them. The young Rhesus, as
I saw, was greatly discontented at being thus rejected, and it would, like
a naughty child, annoy and attack the young drill and mandrill whenever it
could do so with safety; this conduct exciting great indignation in the old
baboon. Monkeys will also, according to Brehm, defend their master when
attacked by any one, as well as dogs to whom they are attached, from the
attacks of other dogs. But we here trench on the subjects of sympathy and
fidelity, to which I shall recur. Some of Brehm's monkeys took much
delight in teasing a certain old dog whom they disliked, as well as other
animals, in various ingenious ways.
Most of the more complex emotions are common to the higher animals and
ourselves. Every one has seen how jealous a dog is of his master's
affection, if lavished on any other creature; and I have observed the same
fact with monkeys. This shews that animals not only love, but have desire
to be loved. Animals manifestly feel emulation. They love approbation or
praise; and a dog carrying a basket for his master exhibits in a high
degree self-complacency or pride. There can, I think, be no doubt that a
dog feels shame, as distinct from fear, and something very like modesty
when begging too often for food. A great dog scorns the snarling of a
little dog, and this may be called magnanimity. Several observers have
stated that monkeys certainly dislike being laughed at; and they sometimes
invent imaginary offences. In the Zoological Gardens I saw a baboon who
always got into a furious rage when his keeper took out a letter or book
and read it aloud to him; and his rage was so violent that, as I witnessed
on one occasion, he bit his own leg till the blood flowed. Dogs shew what
may be fairly called a sense of humour, as distinct from mere play; if a
bit of stick or other such object be thrown to one, he will often carry it
away for a short distance; and then squatting down with it on the ground
close before him, will wait until his master comes quite close to take it
away. The dog will then seize it and rush away in triumph, repeating the
same manoeuvre, and evidently enjoying the practical joke.
We will now turn to the more intellectual emotions and faculties, which are
very important, as forming the basis for the development of the higher
mental powers. Animals manifestly enjoy excitement, and suffer from ennui,
as may be seen with dogs, and, according to Rengger, with monkeys. All
animals feel WONDER, and many exhibit CURIOSITY. They sometimes suffer
from this latter quality, as when the hunter plays antics and thus attracts
them; I have witnessed this with deer, and so it is with the wary chamois,
and with some kinds of wild-ducks. Brehm gives a curious account of the
instinctive dread, which his monkeys exhibited, for snakes; but their
curiosity was so great that they could not desist from occasionally
satiating their horror in a most human fashion, by lifting up the lid of
the box in which the snakes were kept. I was so much surprised at his
account, that I took a stuffed and coiled-up snake into the monkey-house at
the Zoological Gardens, and the excitement thus caused was one of the most
curious spectacles which I ever beheld. Three species of Cercopithecus
were the most alarmed; they dashed about their cages, and uttered sharp
signal cries of danger, which were understood by the other monkeys. A few
young monkeys and one old Anubis baboon alone took no notice of the snake.
I then placed the stuffed specimen on the ground in one of the larger
compartments. After a time all the monkeys collected round it in a large
circle, and staring intently, presented a most ludicrous appearance. They
became extremely nervous; so that when a wooden ball, with which they were
familiar as a plaything, was accidentally moved in the straw, under which
it was partly hidden, they all instantly started away. These monkeys
behaved very differently when a dead fish, a mouse (12. I have given a
short account of their behaviour on this occasion in my 'Expression of the
Emotions in Man and Animals,' p. 43.), a living turtle, and other new
objects were placed in their cages; for though at first frightened, they
soon approached, handled and examined them. I then placed a live snake in
a paper bag, with the mouth loosely closed, in one of the larger
compartments. One of the monkeys immediately approached, cautiously opened
the bag a little, peeped in, and instantly dashed away. Then I witnessed
what Brehm has described, for monkey after monkey, with head raised high
and turned on one side, could not resist taking a momentary peep into the
upright bag, at the dreadful object lying quietly at the bottom. It would
almost appear as if monkeys had some notion of zoological affinities, for
those kept by Brehm exhibited a strange, though mistaken, instinctive dread
of innocent lizards and frogs. An orang, also, has been known to be much
alarmed at the first sight of a turtle. (13. W.C.L. Martin, 'Natural
History of Mammalia,' 1841, p. 405.)
The principle of IMITATION is strong in man, and especially, as I have
myself observed, with savages. In certain morbid states of the brain this
tendency is exaggerated to an extraordinary degree: some hemiplegic
patients and others, at the commencement of inflammatory softening of the
brain, unconsciously imitate every word which is uttered, whether in their
own or in a foreign language, and every gesture or action which is
performed near them. (14. Dr. Bateman, 'On Aphasia,' 1870, p. 110.)
Desor (15. Quoted by Vogt, 'Memoire sur les Microcephales,' 1867, p. 168.)
has remarked that no animal voluntarily imitates an action performed by
man, until in the ascending scale we come to monkeys, which are well known
to be ridiculous mockers. Animals, however, sometimes imitate each other's
actions: thus two species of wolves, which had been reared by dogs,
learned to bark, as does sometimes the jackal (16. The 'Variation of
Animals and Plants under Domestication,' vol. i. p. 27.), but whether this
can be called voluntary imitation is another question. Birds imitate the
songs of their parents, and sometimes of other birds; and parrots are
notorious imitators of any sound which they often hear. Dureau de la Malle
gives an account (17. 'Annales des Sciences Nat.' (1st Series), tom. xxii.
p. 397.) of a dog reared by a cat, who learnt to imitate the well-known
action of a cat licking her paws, and thus washing her ears and face; this
was also witnessed by the celebrated naturalist Audouin. I have received
several confirmatory accounts; in one of these, a dog had not been suckled
by a cat, but had been brought up with one, together with kittens, and had
thus acquired the above habit, which he ever afterwards practised during
his life of thirteen years. Dureau de la Malle's dog likewise learnt from
the kittens to play with a ball by rolling it about with his fore paws, and
springing on it. A correspondent assures me that a cat in his house used
to put her paws into jugs of milk having too narrow a mouth for her head.
A kitten of this cat soon learned the same trick, and practised it ever
afterwards, whenever there was an opportunity.
The parents of many animals, trusting to the principle of imitation in
their young, and more especially to their instinctive or inherited
tendencies, may be said to educate them. We see this when a cat brings a
live mouse to her kittens; and Dureau de la Malle has given a curious
account (in the paper above quoted) of his observations on hawks which
taught their young dexterity, as well as judgment of distances, by first
dropping through the air dead mice and sparrows, which the young generally
failed to catch, and then bringing them live birds and letting them loose.
Hardly any faculty is more important for the intellectual progress of man
than ATTENTION. Animals clearly manifest this power, as when a cat watches
by a hole and prepares to spring on its prey. Wild animals sometimes
become so absorbed when thus engaged, that they may be easily approached.
Mr. Bartlett has given me a curious proof how variable this faculty is in
monkeys. A man who trains monkeys to act in plays, used to purchase common
kinds from the Zoological Society at the price of five pounds for each; but
he offered to give double the price, if he might keep three or four of them
for a few days, in order to select one. When asked how he could possibly
learn so soon, whether a particular monkey would turn out a good actor, he
answered that it all depended on their power of attention. If when he was
talking and explaining anything to a monkey, its attention was easily
distracted, as by a fly on the wall or other trifling object, the case was
hopeless. If he tried by punishment to make an inattentive monkey act, it
turned sulky. On the other hand, a monkey which carefully attended to him
could always be trained.
It is almost superfluous to state that animals have excellent MEMORIES for
persons and places. A baboon at the Cape of Good Hope, as I have been
informed by Sir Andrew Smith, recognised him with joy after an absence of
nine months. I had a dog who was savage and averse to all strangers, and I
purposely tried his memory after an absence of five years and two days. I
went near the stable where he lived, and shouted to him in my old manner;
he shewed no joy, but instantly followed me out walking, and obeyed me,
exactly as if I had parted with him only half an hour before. A train of
old associations, dormant during five years, had thus been instantaneously
awakened in his mind. Even ants, as P. Huber (18. 'Les Moeurs des
Fourmis,' 1810, p. 150.) has clearly shewn, recognised their fellow-ants
belonging to the same community after a separation of four months. Animals
can certainly by some means judge of the intervals of time between
recurrent events.
The IMAGINATION is one of the highest prerogatives of man. By this faculty
he unites former images and ideas, independently of the will, and thus
creates brilliant and novel results. A poet, as Jean Paul Richter remarks
(19. Quoted in Dr. Maudsley's 'Physiology and Pathology of Mind,' 1868,
pp. 19, 220.), "who must reflect whether he shall make a character say yes
or no--to the devil with him; he is only a stupid corpse." Dreaming gives
us the best notion of this power; as Jean Paul again says, "The dream is an
involuntary art of poetry." The value of the products of our imagination
depends of course on the number, accuracy, and clearness of our
impressions, on our judgment and taste in selecting or rejecting the
involuntary combinations, and to a certain extent on our power of
voluntarily combining them. As dogs, cats, horses, and probably all the
higher animals, even birds (20. Dr. Jerdon, 'Birds of India,' vol. i.
1862, p. xxi. Houzeau says that his parokeets and canary-birds dreamt:
'Etudes sur les Facultes Mentales des Animaux,' tom. ii. p. 136.) have
vivid dreams, and this is shewn by their movements and the sounds uttered,
we must admit that they possess some power of imagination. There must be
something special, which causes dogs to howl in the night, and especially
during moonlight, in that remarkable and melancholy manner called baying.
All dogs do not do so; and, according to Houzeau (21. ibid. 1872, tom. ii.
p. 181.), they do not then look at the moon, but at some fixed point near
the horizon. Houzeau thinks that their imaginations are disturbed by the
vague outlines of the surrounding objects, and conjure up before them
fantastic images: if this be so, their feelings may almost be called
superstitious.
Of all the faculties of the human mind, it will, I presume, be admitted
that REASON stands at the summit. Only a few persons now dispute that
animals possess some power of reasoning. Animals may constantly be seen to
pause, deliberate, and resolve. It is a significant fact, that the more
the habits of any particular animal are studied by a naturalist, the more
he attributes to reason and the less to unlearnt instincts. (22. Mr. L.H.
Morgan's work on 'The American Beaver,' 1868, offers a good illustration of
this remark. I cannot help thinking, however, that he goes too far in
underrating the power of instinct.) In future chapters we shall see that
some animals extremely low in the scale apparently display a certain amount
of reason. No doubt it is often difficult to distinguish between the power
of reason and that of instinct. For instance, Dr. Hayes, in his work on
'The Open Polar Sea,' repeatedly remarks that his dogs, instead of
continuing to draw the sledges in a compact body, diverged and separated
when they came to thin ice, so that their weight might be more evenly
distributed. This was often the first warning which the travellers
received that the ice was becoming thin and dangerous. Now, did the dogs
act thus from the experience of each individual, or from the example of the
older and wiser dogs, or from an inherited habit, that is from instinct?
This instinct, may possibly have arisen since the time, long ago, when dogs
were first employed by the natives in drawing their sledges; or the Arctic
wolves, the parent-stock of the Esquimaux dog, may have acquired an
instinct impelling them not to attack their prey in a close pack, when on
thin ice.
We can only judge by the circumstances under which actions are performed,
whether they are due to instinct, or to reason, or to the mere association
of ideas: this latter principle, however, is intimately connected with
reason. A curious case has been given by Prof. Mobius (23. 'Die
Bewegungen der Thiere,' etc., 1873, p. 11.), of a pike, separated by a
plate of glass from an adjoining aquarium stocked with fish, and who often
dashed himself with such violence against the glass in trying to catch the
other fishes, that he was sometimes completely stunned. The pike went on
thus for three months, but at last learnt caution, and ceased to do so.
The plate of glass was then removed, but the pike would not attack these
particular fishes, though he would devour others which were afterwards
introduced; so strongly was the idea of a violent shock associated in his
feeble mind with the attempt on his former neighbours. If a savage, who
had never seen a large plate-glass window, were to dash himself even once
against it, he would for a long time afterwards associate a shock with a
window-frame; but very differently from the pike, he would probably reflect
on the nature of the impediment, and be cautious under analogous
circumstances. Now with monkeys, as we shall presently see, a painful or
merely a disagreeable impression, from an action once performed, is
sometimes sufficient to prevent the animal from repeating it. If we
attribute this difference between the monkey and the pike solely to the
association of ideas being so much stronger and more persistent in the one
than the other, though the pike often received much the more severe injury,
can we maintain in the case of man that a similar difference implies the
possession of a fundamentally different mind?
Houzeau relates (24. 'Etudes sur les Facultes Mentales des Animaux,' 1872,
tom. ii. p. 265.) that, whilst crossing a wide and arid plain in Texas, his
two dogs suffered greatly from thirst, and that between thirty and forty
times they rushed down the hollows to search for water. These hollows were
not valleys, and there were no trees in them, or any other difference in
the vegetation, and as they were absolutely dry there could have been no
smell of damp earth. The dogs behaved as if they knew that a dip in the
ground offered them the best chance of finding water, and Houzeau has often
witnessed the same behaviour in other animals.
I have seen, as I daresay have others, that when a small object is thrown
on the ground beyond the reach of one of the elephants in the Zoological
Gardens, he blows through his trunk on the ground beyond the object, so
that the current reflected on all sides may drive the object within his
reach. Again a well-known ethnologist, Mr. Westropp, informs me that he
observed in Vienna a bear deliberately making with his paw a current in
some water, which was close to the bars of his cage, so as to draw a piece
of floating bread within his reach. These actions of the elephant and bear
can hardly be attributed to instinct or inherited habit, as they would be
of little use to an animal in a state of nature. Now, what is the
difference between such actions, when performed by an uncultivated man, and
by one of the higher animals?
The savage and the dog have often found water at a low level, and the
coincidence under such circumstances has become associated in their minds.
A cultivated man would perhaps make some general proposition on the
subject; but from all that we know of savages it is extremely doubtful
whether they would do so, and a dog certainly would not. But a savage, as
well as a dog, would search in the same way, though frequently
disappointed; and in both it seems to be equally an act of reason, whether
or not any general proposition on the subject is consciously placed before
the mind. (25. Prof. Huxley has analysed with admirable clearness the
mental steps by which a man, as well as a dog, arrives at a conclusion in a
case analogous to that given in my text. See his article, 'Mr. Darwin's
Critics,' in the 'Contemporary Review,' Nov. 1871, p. 462, and in his
'Critiques and Essays,' 1873, p. 279.) The same would apply to the
elephant and the bear making currents in the air or water. The savage
would certainly neither know nor care by what law the desired movements
were effected; yet his act would be guided by a rude process of reasoning,
as surely as would a philosopher in his longest chain of deductions. There
would no doubt be this difference between him and one of the higher
animals, that he would take notice of much slighter circumstances and
conditions, and would observe any connection between them after much less
experience, and this would be of paramount importance. I kept a daily
record of the actions of one of my infants, and when he was about eleven
months old, and before he could speak a single word, I was continually
struck with the greater quickness, with which all sorts of objects and
sounds were associated together in his mind, compared with that of the most
intelligent dogs I ever knew. But the higher animals differ in exactly the
same way in this power of association from those low in the scale, such as
the pike, as well as in that of drawing inferences and of observation.
The promptings of reason, after very short experience, are well shewn by
the following actions of American monkeys, which stand low in their order.
Rengger, a most careful observer, states that when he first gave eggs to
his monkeys in Paraguay, they smashed them, and thus lost much of their
contents; afterwards they gently hit one end against some hard body, and
picked off the bits of shell with their fingers. After cutting themselves
only ONCE with any sharp tool, they would not touch it again, or would
handle it with the greatest caution. Lumps of sugar were often given them
wrapped up in paper; and Rengger sometimes put a live wasp in the paper, so
that in hastily unfolding it they got stung; after this had ONCE happened,
they always first held the packet to their ears to detect any movement
within. (26. Mr. Belt, in his most interesting work, 'The Naturalist in
Nicaragua,' 1874, (p. 119,) likewise describes various actions of a tamed
Cebus, which, I think, clearly shew that this animal possessed some
reasoning power.)
The following cases relate to dogs. Mr. Colquhoun (27. 'The Moor and the
Loch,' p. 45. Col. Hutchinson on 'Dog Breaking,' 1850, p. 46.) winged two
wild-ducks, which fell on the further side of a stream; his retriever tried
to bring over both at once, but could not succeed; she then, though never
before known to ruffle a feather, deliberately killed one, brought over the
other, and returned for the dead bird. Col. Hutchinson relates that two
partridges were shot at once, one being killed, the other wounded; the
latter ran away, and was caught by the retriever, who on her return came
across the dead bird; "she stopped, evidently greatly puzzled, and after
one or two trials, finding she could not take it up without permitting the
escape of the winged bird, she considered a moment, then deliberately
murdered it by giving it a severe crunch, and afterwards brought away both
together. This was the only known instance of her ever having wilfully
injured any game." Here we have reason though not quite perfect, for the
retriever might have brought the wounded bird first and then returned for
the dead one, as in the case of the two wild-ducks. I give the above
cases, as resting on the evidence of two independent witnesses, and because
in both instances the retrievers, after deliberation, broke through a habit
which is inherited by them (that of not killing the game retrieved), and
because they shew how strong their reasoning faculty must have been to
overcome a fixed habit.
I will conclude by quoting a remark by the illustrious Humboldt. (28.
'Personal Narrative,' Eng. translat., vol. iii. p. 106.) "The muleteers in
S. America say, 'I will not give you the mule whose step is easiest, but la
mas racional,--the one that reasons best'"; and; as, he adds, "this popular
expression, dictated by long experience, combats the system of animated
machines, better perhaps than all the arguments of speculative philosophy."
Nevertheless some writers even yet deny that the higher animals possess a
trace of reason; and they endeavour to explain away, by what appears to be
mere verbiage, (29. I am glad to find that so acute a reasoner as Mr.
Leslie Stephen ('Darwinism and Divinity, Essays on Free Thinking,' 1873, p.
80), in speaking of the supposed impassable barrier between the minds of
man and the lower animals, says, "The distinctions, indeed, which have been
drawn, seem to us to rest upon no better foundation than a great many other
metaphysical distinctions; that is, the assumption that because you can
give two things different names, they must therefore have different
natures. It is difficult to understand how anybody who has ever kept a
dog, or seen an elephant, can have any doubt as to an animal's power of
performing the essential processes of reasoning.") all such facts as those
above given.
It has, I think, now been shewn that man and the higher animals, especially
the Primates, have some few instincts in common. All have the same senses,
intuitions, and sensations,--similar passions, affections, and emotions,
even the more complex ones, such as jealousy, suspicion, emulation,
gratitude, and magnanimity; they practise deceit and are revengeful; they
are sometimes susceptible to ridicule, and even have a sense of humour;
they feel wonder and curiosity; they possess the same faculties of
imitation, attention, deliberation, choice, memory, imagination, the
association of ideas, and reason, though in very different degrees. The
individuals of the same species graduate in intellect from absolute
imbecility to high excellence. They are also liable to insanity, though
far less often than in the case of man. (30. See 'Madness in Animals,' by
Dr. W. Lauder Lindsay, in 'Journal of Mental Science,' July 1871.)
Nevertheless, many authors have insisted that man is divided by an
insuperable barrier from all the lower animals in his mental faculties. I
formerly made a collection of above a score of such aphorisms, but they are
almost worthless, as their wide difference and number prove the difficulty,
if not the impossibility, of the attempt. It has been asserted that man
alone is capable of progressive improvement; that he alone makes use of
tools or fire, domesticates other animals, or possesses property; that no
animal has the power of abstraction, or of forming general concepts, is
self-conscious and comprehends itself; that no animal employs language;
that man alone has a sense of beauty, is liable to caprice, has the feeling
of gratitude, mystery, etc.; believes in God, or is endowed with a
conscience. I will hazard a few remarks on the more important and
interesting of these points.
Archbishop Sumner formerly maintained (31. Quoted by Sir C. Lyell,
'Antiquity of Man,' p. 497.) that man alone is capable of progressive
improvement. That he is capable of incomparably greater and more rapid
improvement than is any other animal, admits of no dispute; and this is
mainly due to his power of speaking and handing down his acquired
knowledge. With animals, looking first to the individual, every one who
has had any experience in setting traps, knows that young animals can he
caught much more easily than old ones; and they can be much more easily
approached by an enemy. Even with respect to old animals, it is impossible
to catch many in the same place and in the same kind of trap, or to destroy
them by the same kind of poison; yet it is improbable that all should have
partaken of the poison, and impossible that all should have been caught in
a trap. They must learn caution by seeing their brethren caught or
poisoned. In North America, where the fur-bearing animals have long been
pursued, they exhibit, according to the unanimous testimony of all
observers, an almost incredible amount of sagacity, caution and cunning;
but trapping has been there so long carried on, that inheritance may
possibly have come into play. I have received several accounts that when
telegraphs are first set up in any district, many birds kill themselves by
flying against the wires, but that in the course of a very few years they
learn to avoid this danger, by seeing, as it would appear, their comrades
killed. (32. For additional evidence, with details, see M. Houzeau,
'Etudes sur les Facultes Mentales des Animaux,' tom. ii. 1872, p. 147.)
If we look to successive generations, or to the race, there is no doubt
that birds and other animals gradually both acquire and lose caution in
relation to man or other enemies (33. See, with respect to birds on
oceanic islands, my 'Journal of Researches during the Voyage of the
"Beagle,"' 1845, p. 398. 'Origin of Species,' 5th ed. p. 260.); and this
caution is certainly in chief part an inherited habit or instinct, but in
part the result of individual experience. A good observer, Leroy (34.
'Lettres Phil. sur l'Intelligence des Animaux,' nouvelle edit., 1802, p.
86.), states, that in districts where foxes are much hunted, the young, on
first leaving their burrows, are incontestably much more wary than the old
ones in districts where they are not much disturbed.
Our domestic dogs are descended from wolves and jackals (35. See the
evidence on this head in chap. i. vol. i., 'On the Variation of Animals and
Plants under Domestication.'), and though they may not have gained in
cunning, and may have lost in wariness and suspicion, yet they have
progressed in certain moral qualities, such as in affection, trust-
worthiness, temper, and probably in general intelligence. The common rat
has conquered and beaten several other species throughout Europe, in parts
of North America, New Zealand, and recently in Formosa, as well as on the
mainland of China. Mr. Swinhoe (36. 'Proceedings Zoological Society,'
1864, p. 186.), who describes these two latter cases, attributes the
victory of the common rat over the large Mus coninga to its superior
cunning; and this latter quality may probably be attributed to the habitual
exercise of all its faculties in avoiding extirpation by man, as well as to
nearly all the less cunning or weak-minded rats having been continuously
destroyed by him. It is, however, possible that the success of the common
rat may be due to its having possessed greater cunning than its fellow-
species, before it became associated with man. To maintain, independently
of any direct evidence, that no animal during the course of ages has
progressed in intellect or other mental faculties, is to beg the question
of the evolution of species. We have seen that, according to Lartet,
existing mammals belonging to several orders have larger brains than their
ancient tertiary prototypes.
It has often been said that no animal uses any tool; but the chimpanzee in
a state of nature cracks a native fruit, somewhat like a walnut, with a
stone. (37. Savage and Wyman in 'Boston Journal of Natural History,' vol.
iv. 1843-44, p. 383.) Rengger (38. 'Saugethiere von Paraguay,' 1830, s.
51-56.) easily taught an American monkey thus to break open hard palm-nuts;
and afterwards of its own accord, it used stones to open other kinds of
nuts, as well as boxes. It thus also removed the soft rind of fruit that
had a disagreeable flavour. Another monkey was taught to open the lid of a
large box with a stick, and afterwards it used the stick as a lever to move
heavy bodies; and I have myself seen a young orang put a stick into a
crevice, slip his hand to the other end, and use it in the proper manner as
a lever. The tamed elephants in India are well known to break off branches
of trees and use them to drive away the flies; and this same act has been
observed in an elephant in a state of nature. (39. The Indian Field,
March 4, 1871.) I have seen a young orang, when she thought she was going
to be whipped, cover and protect herself with a blanket or straw. In these
several cases stones and sticks were employed as implements; but they are
likewise used as weapons. Brehm (40. 'Thierleben,' B. i. s. 79, 82.)
states, on the authority of the well-known traveller Schimper, that in
Abyssinia when the baboons belonging to one species (C. gelada) descend in
troops from the mountains to plunder the fields, they sometimes encounter
troops of another species (C. hamadryas), and then a fight ensues. The
Geladas roll down great stones, which the Hamadryas try to avoid, and then
both species, making a great uproar, rush furiously against each other.
Brehm, when accompanying the Duke of Coburg-Gotha, aided in an attack with
fire-arms on a troop of baboons in the pass of Mensa in Abyssinia. The
baboons in return rolled so many stones down the mountain, some as large as
a man's head, that the attackers had to beat a hasty retreat; and the pass
was actually closed for a time against the caravan. It deserves notice
that these baboons thus acted in concert. Mr. Wallace (41. 'The Malay
Archipelago,' vol. i. 1869, p. 87.) on three occasions saw female orangs,
accompanied by their young, "breaking off branches and the great spiny
fruit of the Durian tree, with every appearance of rage; causing such a
shower of missiles as effectually kept us from approaching too near the
tree." As I have repeatedly seen, a chimpanzee will throw any object at
hand at a person who offends him; and the before-mentioned baboon at the
Cape of Good Hope prepared mud for the purpose.
In the Zoological Gardens, a monkey, which had weak teeth, used to break
open nuts with a stone; and I was assured by the keepers that after using
the stone, he hid it in the straw, and would not let any other monkey touch
it. Here, then, we have the idea of property; but this idea is common to
every dog with a bone, and to most or all birds with their nests.
The Duke of Argyll (42. 'Primeval Man,' 1869, pp. 145, 147.) remarks, that
the fashioning of an implement for a special purpose is absolutely peculiar
to man; and he considers that this forms an immeasurable gulf between him
and the brutes. This is no doubt a very important distinction; but there
appears to me much truth in Sir J. Lubbock's suggestion (43. 'Prehistoric
Times,' 1865, p. 473, etc.), that when primeval man first used flint-stones
for any purpose, he would have accidentally splintered them, and would then
have used the sharp fragments. From this step it would be a small one to
break the flints on purpose, and not a very wide step to fashion them
rudely. This latter advance, however, may have taken long ages, if we may
judge by the immense interval of time which elapsed before the men of the
neolithic period took to grinding and polishing their stone tools. In
breaking the flints, as Sir J. Lubbock likewise remarks, sparks would have
been emitted, and in grinding them heat would have been evolved: thus the
two usual methods of "obtaining fire may have originated." The nature of
fire would have been known in the many volcanic regions where lava
occasionally flows through forests. The anthropomorphous apes, guided
probably by instinct, build for themselves temporary platforms; but as many
instincts are largely controlled by reason, the simpler ones, such as this
of building a platform, might readily pass into a voluntary and conscious
act. The orang is known to cover itself at night with the leaves of the
Pandanus; and Brehm states that one of his baboons used to protect itself
from the heat of the sun by throwing a straw-mat over its head. In these
several habits, we probably see the first steps towards some of the simpler
arts, such as rude architecture and dress, as they arose amongst the early
progenitors of man.
ABSTRACTION, GENERAL CONCEPTIONS, SELF-CONSCIOUSNESS, MENTAL INDIVIDUALITY.
It would be very difficult for any one with even much more knowledge than I
possess, to determine how far animals exhibit any traces of these high
mental powers. This difficulty arises from the impossibility of judging
what passes through the mind of an animal; and again, the fact that writers
differ to a great extent in the meaning which they attribute to the above
terms, causes a further difficulty. If one may judge from various articles
which have been published lately, the greatest stress seems to be laid on
the supposed entire absence in animals of the power of abstraction, or of
forming general concepts. But when a dog sees another dog at a distance,
it is often clear that he perceives that it is a dog in the abstract; for
when he gets nearer his whole manner suddenly changes, if the other dog be
a friend. A recent writer remarks, that in all such cases it is a pure
assumption to assert that the mental act is not essentially of the same
nature in the animal as in man. If either refers what he perceives with
his senses to a mental concept, then so do both. (44. Mr. Hookham, in a
letter to Prof. Max Muller, in the 'Birmingham News,' May 1873.) When I
say to my terrier, in an eager voice (and I have made the trial many
times), "Hi, hi, where is it?" she at once takes it as a sign that
something is to be hunted, and generally first looks quickly all around,
and then rushes into the nearest thicket, to scent for any game, but
finding nothing, she looks up into any neighbouring tree for a squirrel.
Now do not these actions clearly shew that she had in her mind a general
idea or concept that some animal is to be discovered and hunted?
It may be freely admitted that no animal is self-conscious, if by this term
it is implied, that he reflects on such points, as whence he comes or
whither he will go, or what is life and death, and so forth. But how can
we feel sure that an old dog with an excellent memory and some power of
imagination, as shewn by his dreams, never reflects on his past pleasures
or pains in the chase? And this would be a form of self-consciousness. On
the other hand, as Buchner (45. 'Conferences sur la Theorie Darwinienne,'
French translat. 1869, p. 132.) has remarked, how little can the hard-
worked wife of a degraded Australian savage, who uses very few abstract
words, and cannot count above four, exert her self-consciousness, or
reflect on the nature of her own existence. It is generally admitted, that
the higher animals possess memory, attention, association, and even some
imagination and reason. If these powers, which differ much in different
animals, are capable of improvement, there seems no great improbability in
more complex faculties, such as the higher forms of abstraction, and self-
consciousness, etc., having been evolved through the development and
combination of the simpler ones. It has been urged against the views here
maintained that it is impossible to say at what point in the ascending
scale animals become capable of abstraction, etc.; but who can say at what
age this occurs in our young children? We see at least that such powers
are developed in children by imperceptible degrees.
That animals retain their mental individuality is unquestionable. When my
voice awakened a train of old associations in the mind of the before-
mentioned dog, he must have retained his mental individuality, although
every atom of his brain had probably undergone change more than once during
the interval of five years. This dog might have brought forward the
argument lately advanced to crush all evolutionists, and said, "I abide
amid all mental moods and all material changes...The teaching that atoms
leave their impressions as legacies to other atoms falling into the places
they have vacated is contradictory of the utterance of consciousness, and
is therefore false; but it is the teaching necessitated by evolutionism,
consequently the hypothesis is a false one." (46. The Rev. Dr. J. M'Cann,
'Anti-Darwinism,' 1869, p. 13.)
LANGUAGE.
This faculty has justly been considered as one of the chief distinctions
between man and the lower animals. But man, as a highly competent judge,
Archbishop Whately remarks, "is not the only animal that can make use of
language to express what is passing in his mind, and can understand, more
or less, what is so expressed by another." (47. Quoted in
'Anthropological Review,' 1864, p. 158.) In Paraguay the Cebus azarae when
excited utters at least six distinct sounds, which excite in other monkeys
similar emotions. (48. Rengger, ibid. s. 45.) The movements of the
features and gestures of monkeys are understood by us, and they partly
understand ours, as Rengger and others declare. It is a more remarkable
fact that the dog, since being domesticated, has learnt to bark (49. See
my 'Variation of Animals and Plants under Domestication,' vol. i. p. 27.)
in at least four or five distinct tones. Although barking is a new art, no
doubt the wild parent-species of the dog expressed their feelings by cries
of various kinds. With the domesticated dog we have the bark of eagerness,
as in the chase; that of anger, as well as growling; the yelp or howl of
despair, as when shut up; the baying at night; the bark of joy, as when
starting on a walk with his master; and the very distinct one of demand or
supplication, as when wishing for a door or window to be opened. According
to Houzeau, who paid particular attention to the subject, the domestic fowl
utters at least a dozen significant sounds. (50. 'Facultes Mentales des
Animaux,' tom. ii. 1872, p. 346-349.)
The habitual use of articulate language is, however, peculiar to man; but
he uses, in common with the lower animals, inarticulate cries to express
his meaning, aided by gestures and the movements of the muscles of the
face. (51. See a discussion on this subject in Mr. E.B. Tylor's very
interesting work, 'Researches into the Early History of Mankind,' 1865,
chaps. ii. to iv.) This especially holds good with the more simple and
vivid feelings, which are but little connected with our higher
intelligence. Our cries of pain, fear, surprise, anger, together with
their appropriate actions, and the murmur of a mother to her beloved child
are more expressive than any words. That which distinguishes man from the
lower animals is not the understanding of articulate sounds, for, as every
one knows, dogs understand many words and sentences. In this respect they
are at the same stage of development as infants, between the ages of ten
and twelve months, who understand many words and short sentences, but
cannot yet utter a single word. It is not the mere articulation which is
our distinguishing character, for parrots and other birds possess this
power. Nor is it the mere capacity of connecting definite sounds with
definite ideas; for it is certain that some parrots, which have been taught
to speak, connect unerringly words with things, and persons with events.
(52. I have received several detailed accounts to this effect. Admiral
Sir B.J. Sulivan, whom I know to be a careful observer, assures me that an
African parrot, long kept in his father's house, invariably called certain
persons of the household, as well as visitors, by their names. He said
"good morning" to every one at breakfast, and "good night" to each as they
left the room at night, and never reversed these salutations. To Sir B.J.
Sulivan's father, he used to add to the " good morning" a short sentence,
which was never once repeated after his father's death. He scolded
violently a strange dog which came into the room through the open window;
and he scolded another parrot (saying "you naughty polly") which had got
out of its cage, and was eating apples on the kitchen table. See also, to
the same effect, Houzeau on parrots, 'Facultes Mentales,' tom. ii. p. 309.
Dr. A. Moschkau informs me that he knew a starling which never made a
mistake in saying in German "good morning" to persons arriving, and "good
bye, old fellow," to those departing. I could add several other such
cases.) The lower animals differ from man solely in his almost infinitely
larger power of associating together the most diversified sounds and ideas;
and this obviously depends on the high development of his mental powers.
As Horne Tooke, one of the founders of the noble science of philology,
observes, language is an art, like brewing or baking; but writing would
have been a better simile. It certainly is not a true instinct, for every
language has to be learnt. It differs, however, widely from all ordinary
arts, for man has an instinctive tendency to speak, as we see in the babble
of our young children; whilst no child has an instinctive tendency to brew,
bake, or write. Moreover, no philologist now supposes that any language
has been deliberately invented; it has been slowly and unconsciously
developed by many steps. (53. See some good remarks on this head by Prof.
Whitney, in his 'Oriental and Linguistic Studies,' 1873, p. 354. He
observes that the desire of communication between man is the living force,
which, in the development of language, "works both consciously and
unconsciously; consciously as regards the immediate end to be attained;
unconsciously as regards the further consequences of the act.") The sounds
uttered by birds offer in several respects the nearest analogy to language,
for all the members of the same species utter the same instinctive cries
expressive of their emotions; and all the kinds which sing, exert their
power instinctively; but the actual song, and even the call-notes, are
learnt from their parents or foster-parents. These sounds, as Daines
Barrington (54. Hon. Daines Barrington in 'Philosoph. Transactions,' 1773,
p. 262. See also Dureau de la Malle, in 'Ann. des. Sc. Nat.' 3rd series,
Zoolog., tom. x. p. 119.) has proved, "are no more innate than language is
in man." The first attempts to sing "may be compared to the imperfect
endeavour in a child to babble." The young males continue practising, or
as the bird-catchers say, "recording," for ten or eleven months. Their
first essays shew hardly a rudiment of the future song; but as they grow
older we can perceive what they are aiming at; and at last they are said
"to sing their song round." Nestlings which have learnt the song of a
distinct species, as with the canary-birds educated in the Tyrol, teach and
transmit their new song to their offspring. The slight natural differences
of song in the same species inhabiting different districts may be
appositely compared, as Barrington remarks, "to provincial dialects"; and
the songs of allied, though distinct species may be compared with the
languages of distinct races of man. I have given the foregoing details to
shew that an instinctive tendency to acquire an art is not peculiar to man.
With respect to the origin of articulate language, after having read on the
one side the highly interesting works of Mr. Hensleigh Wedgwood, the Rev.
F. Farrar, and Prof. Schleicher (55. 'On the Origin of Language,' by H.
Wedgwood, 1866. 'Chapters on Language,' by the Rev. F.W. Farrar, 1865.
These works are most interesting. See also 'De la Phys. et de Parole,' par
Albert Lemoine, 1865, p. 190. The work on this subject, by the late Prof.
Aug. Schleicher, has been translated by Dr. Bikkers into English, under the
title of 'Darwinism tested by the Science of Language,' 1869.), and the
celebrated lectures of Prof. Max Muller on the other side, I cannot doubt
that language owes its origin to the imitation and modification of various
natural sounds, the voices of other animals, and man's own instinctive
cries, aided by signs and gestures. When we treat of sexual selection we
shall see that primeval man, or rather some early progenitor of man,
probably first used his voice in producing true musical cadences, that is
in singing, as do some of the gibbon-apes at the present day; and we may
conclude from a widely-spread analogy, that this power would have been
especially exerted during the courtship of the sexes,--would have expressed
various emotions, such as love, jealousy, triumph,--and would have served
as a challenge to rivals. It is, therefore, probable that the imitation of
musical cries by articulate sounds may have given rise to words expressive
of various complex emotions. The strong tendency in our nearest allies,
the monkeys, in microcephalous idiots (56. Vogt, 'Memoire sur les
Microcephales,' 1867, p. 169. With respect to savages, I have given some
facts in my 'Journal of Researches,' etc., 1845, p. 206.), and in the
barbarous races of mankind, to imitate whatever they hear deserves notice,
as bearing on the subject of imitation. Since monkeys certainly understand
much that is said to them by man, and when wild, utter signal-cries of
danger to their fellows (57. See clear evidence on this head in the two
works so often quoted, by Brehm and Rengger.); and since fowls give
distinct warnings for danger on the ground, or in the sky from hawks (both,
as well as a third cry, intelligible to dogs) (58. Houzeau gives a very
curious account of his observations on this subject in his 'Facultes
Mentales des Animaux,' tom. ii. p. 348.), may not some unusually wise ape-
like animal have imitated the growl of a beast of prey, and thus told his
fellow-monkeys the nature of the expected danger? This would have been a
first step in the formation of a language.
As the voice was used more and more, the vocal organs would have been
strengthened and perfected through the principle of the inherited effects
of use; and this would have reacted on the power of speech. But the
relation between the continued use of language and the development of the
brain, has no doubt been far more important. The mental powers in some
early progenitor of man must have been more highly developed than in any
existing ape, before even the most imperfect form of speech could have come
into use; but we may confidently believe that the continued use and
advancement of this power would have reacted on the mind itself, by
enabling and encouraging it to carry on long trains of thought. A complex
train of thought can no more be carried on without the aid of words,
whether spoken or silent, than a long calculation without the use of
figures or algebra. It appears, also, that even an ordinary train of
thought almost requires, or is greatly facilitated by some form of
language, for the dumb, deaf, and blind girl, Laura Bridgman, was observed
to use her fingers whilst dreaming. (59. See remarks on this head by Dr.
Maudsley, 'The Physiology and Pathology of Mind,' 2nd ed., 1868, p. 199.)
Nevertheless, a long succession of vivid and connected ideas may pass
through the mind without the aid of any form of language, as we may infer
from the movements of dogs during their dreams. We have, also, seen that
animals are able to reason to a certain extent, manifestly without the aid
of language. The intimate connection between the brain, as it is now
developed in us, and the faculty of speech, is well shewn by those curious
cases of brain-disease in which speech is specially affected, as when the
power to remember substantives is lost, whilst other words can be correctly
used, or where substantives of a certain class, or all except the initial
letters of substantives and proper names are forgotten. (60. Many curious
cases have been recorded. See, for instance, Dr. Bateman 'On Aphasia,'
1870, pp. 27, 31, 53, 100, etc. Also, 'Inquiries Concerning the
Intellectual Powers,' by Dr. Abercrombie, 1838, p. 150.) There is no more
improbability in the continued use of the mental and vocal organs leading
to inherited changes in their structure and functions, than in the case of
hand-writing, which depends partly on the form of the hand and partly on
the disposition of the mind; and handwriting is certainly inherited. (61.
'The Variation of Animals and Plants under Domestication,' vol. ii. p. 6.'
Several writers, more especially Prof. Max Muller (62. Lectures on 'Mr.
Darwin's Philosophy of Language,' 1873.), have lately insisted that the use
of language implies the power of forming general concepts; and that as no
animals are supposed to possess this power, an impassable barrier is formed
between them and man. (63. The judgment of a distinguished philologist,
such as Prof. Whitney, will have far more weight on this point than
anything that I can say. He remarks ('Oriental and Linguistic Studies,'
1873, p. 297), in speaking of Bleek's views: "Because on the grand scale
language is the necessary auxiliary of thought, indispensable to the
development of the power of thinking, to the distinctness and variety and
complexity of cognitions to the full mastery of consciousness; therefore he
would fain make thought absolutely impossible without speech, identifying
the faculty with its instrument. He might just as reasonably assert that
the human hand cannot act without a tool. With such a doctrine to start
from, he cannot stop short of Max Muller's worst paradoxes, that an infant
(in fans, not speaking) is not a human being, and that deaf-mutes do not
become possessed of reason until they learn to twist their fingers into
imitation of spoken words." Max Muller gives in italics ('Lectures on Mr.
Darwin's Philosophy of Language,' 1873, third lecture) this aphorism:
"There is no thought without words, as little as there are words without
thought." What a strange definition must here be given to the word
thought!) With respect to animals, I have already endeavoured to shew that
they have this power, at least in a rude and incipient degree. As far as
concerns infants of from ten to eleven months old, and deaf-mutes, it seems
to me incredible, that they should be able to connect certain sounds with
certain general ideas as quickly as they do, unless such ideas were already
formed in their minds. The same remark may be extended to the more
intelligent animals; as Mr. Leslie Stephen observes (64. 'Essays on Free
Thinking,' etc., 1873, p. 82.), "A dog frames a general concept of cats or
sheep, and knows the corresponding words as well as a philosopher. And the
capacity to understand is as good a proof of vocal intelligence, though in
an inferior degree, as the capacity to speak."
Why the organs now used for speech should have been originally perfected
for this purpose, rather than any other organs, it is not difficult to see.
Ants have considerable powers of intercommunication by means of their
antennae, as shewn by Huber, who devotes a whole chapter to their language.
We might have used our fingers as efficient instruments, for a person with
practice can report to a deaf man every word of a speech rapidly delivered
at a public meeting; but the loss of our hands, whilst thus employed, would
have been a serious inconvenience. As all the higher mammals possess vocal
organs, constructed on the same general plan as ours, and used as a means
of communication, it was obviously probable that these same organs would be
still further developed if the power of communication had to be improved;
and this has been effected by the aid of adjoining and well adapted parts,
namely the tongue and lips. (65. See some good remarks to this effect by
Dr. Maudsley, 'The Physiology and Pathology of Mind,' 1868, p. 199.) The
fact of the higher apes not using their vocal organs for speech, no doubt
depends on their intelligence not having been sufficiently advanced. The
possession by them of organs, which with long-continued practice might have
been used for speech, although not thus used, is paralleled by the case of
many birds which possess organs fitted for singing, though they never sing.
Thus, the nightingale and crow have vocal organs similarly constructed,
these being used by the former for diversified song, and by the latter only
for croaking. (66. Macgillivray, 'Hist. of British Birds,' vol. ii. 1839,
p. 29. An excellent observer, Mr. Blackwall, remarks that the magpie
learns to pronounce single words, and even short sentences, more readily
than almost any other British bird; yet, as he adds, after long and closely
investigating its habits, he has never known it, in a state of nature,
display any unusual capacity for imitation. 'Researches in Zoology,' 1834,
p. 158.) If it be asked why apes have not had their intellects developed
to the same degree as that of man, general causes only can be assigned in
answer, and it is unreasonable to expect any thing more definite,
considering our ignorance with respect to the successive stages of
development through which each creature has passed.
The formation of different languages and of distinct species, and the
proofs that both have been developed through a gradual process, are
curiously parallel. (67. See the very interesting parallelism between the
development of species and languages, given by Sir C. Lyell in 'The
Geological Evidences of the Antiquity of Man,' 1863, chap. xxiii.) But we
can trace the formation of many words further back than that of species,
for we can perceive how they actually arose from the imitation of various
sounds. We find in distinct languages striking homologies due to community
of descent, and analogies due to a similar process of formation. The
manner in which certain letters or sounds change when others change is very
like correlated growth. We have in both cases the reduplication of parts,
the effects of long-continued use, and so forth. The frequent presence of
rudiments, both in languages and in species, is still more remarkable. The
letter m in the word am, means I; so that in the expression I am, a
superfluous and useless rudiment has been retained. In the spelling also
of words, letters often remain as the rudiments of ancient forms of
pronunciation. Languages, like organic beings, can be classed in groups
under groups; and they can be classed either naturally according to
descent, or artificially by other characters. Dominant languages and
dialects spread widely, and lead to the gradual extinction of other
tongues. A language, like a species, when once extinct, never, as Sir C.
Lyell remarks, reappears. The same language never has two birth-places.
Distinct languages may be crossed or blended together. (68. See remarks
to this effect by the Rev. F.W. Farrar, in an interesting article, entitled
'Philology and Darwinism,' in 'Nature,' March 24th, 1870, p. 528.) We see
variability in every tongue, and new words are continually cropping up; but
as there is a limit to the powers of the memory, single words, like whole
languages, gradually become extinct. As Max Muller (69. 'Nature,' January
6th, 1870, p. 257.) has well remarked:--"A struggle for life is constantly
going on amongst the words and grammatical forms in each language. The
better, the shorter, the easier forms are constantly gaining the upper
hand, and they owe their success to their own inherent virtue." To these
more important causes of the survival of certain words, mere novelty and
fashion may be added; for there is in the mind of man a strong love for
slight changes in all things. The survival or preservation of certain
favoured words in the struggle for existence is natural selection.
The perfectly regular and wonderfully complex construction of the languages
of many barbarous nations has often been advanced as a proof, either of the
divine origin of these languages, or of the high art and former
civilisation of their founders. Thus F. von Schlegel writes: "In those
languages which appear to be at the lowest grade of intellectual culture,
we frequently observe a very high and elaborate degree of art in their
grammatical structure. This is especially the case with the Basque and the
Lapponian, and many of the American languages." (70. Quoted by C.S. Wake,
'Chapters on Man,' 1868, p. 101.) But it is assuredly an error to speak of
any language as an art, in the sense of its having been elaborately and
methodically formed. Philologists now admit that conjugations,
declensions, etc., originally existed as distinct words, since joined
together; and as such words express the most obvious relations between
objects and persons, it is not surprising that they should have been used
by the men of most races during the earliest ages. With respect to
perfection, the following illustration will best shew how easily we may
err: a Crinoid sometimes consists of no less than 150,000 pieces of shell
(71. Buckland, 'Bridgewater Treatise,' p. 411.), all arranged with perfect
symmetry in radiating lines; but a naturalist does not consider an animal
of this kind as more perfect than a bilateral one with comparatively few
parts, and with none of these parts alike, excepting on the opposite sides
of the body. He justly considers the differentiation and specialisation of
organs as the test of perfection. So with languages: the most symmetrical
and complex ought not to be ranked above irregular, abbreviated, and
bastardised languages, which have borrowed expressive words and useful
forms of construction from various conquering, conquered, or immigrant
races.
From these few and imperfect remarks I conclude that the extremely complex
and regular construction of many barbarous languages, is no proof that they
owe their origin to a special act of creation. (72. See some good remarks
on the simplification of languages, by Sir J. Lubbock, 'Origin of
Civilisation,' 1870, p. 278.) Nor, as we have seen, does the faculty of
articulate speech in itself offer any insuperable objection to the belief
that man has been developed from some lower form.
SENSE OF BEAUTY.
This sense has been declared to be peculiar to man. I refer here only to
the pleasure given by certain colours, forms, and sounds, and which may
fairly be called a sense of the beautiful; with cultivated men such
sensations are, however, intimately associated with complex ideas and
trains of thought. When we behold a male bird elaborately displaying his
graceful plumes or splendid colours before the female, whilst other birds,
not thus decorated, make no such display, it is impossible to doubt that
she admires the beauty of her male partner. As women everywhere deck
themselves with these plumes, the beauty of such ornaments cannot be
disputed. As we shall see later, the nests of humming-birds, and the
playing passages of bower-birds are tastefully ornamented with gaily-
coloured objects; and this shews that they must receive some kind of
pleasure from the sight of such things. With the great majority of
animals, however, the taste for the beautiful is confined, as far as we can
judge, to the attractions of the opposite sex. The sweet strains poured
forth by many male birds during the season of love, are certainly admired
by the females, of which fact evidence will hereafter be given. If female
birds had been incapable of appreciating the beautiful colours, the
ornaments, and voices of their male partners, all the labour and anxiety
exhibited by the latter in displaying their charms before the females would
have been thrown away; and this it is impossible to admit. Why certain
bright colours should excite pleasure cannot, I presume, be explained, any
more than why certain flavours and scents are agreeable; but habit has
something to do with the result, for that which is at first unpleasant to
our senses, ultimately becomes pleasant, and habits are inherited. With
respect to sounds, Helmholtz has explained to a certain extent on
physiological principles, why harmonies and certain cadences are agreeable.
But besides this, sounds frequently recurring at irregular intervals are
highly disagreeable, as every one will admit who has listened at night to
the irregular flapping of a rope on board ship. The same principle seems
to come into play with vision, as the eye prefers symmetry or figures with
some regular recurrence. Patterns of this kind are employed by even the
lowest savages as ornaments; and they have been developed through sexual
selection for the adornment of some male animals. Whether we can or not
give any reason for the pleasure thus derived from vision and hearing, yet
man and many of the lower animals are alike pleased by the same colours,
graceful shading and forms, and the same sounds.
The taste for the beautiful, at least as far as female beauty is concerned,
is not of a special nature in the human mind; for it differs widely in the
different races of man, and is not quite the same even in the different
nations of the same race. Judging from the hideous ornaments, and the
equally hideous music admired by most savages, it might be urged that their
aesthetic faculty was not so highly developed as in certain animals, for
instance, as in birds. Obviously no animal would be capable of admiring
such scenes as the heavens at night, a beautiful landscape, or refined
music; but such high tastes are acquired through culture, and depend on
complex associations; they are not enjoyed by barbarians or by uneducated
persons.
Many of the faculties, which have been of inestimable service to man for
his progressive advancement, such as the powers of the imagination, wonder,
curiosity, an undefined sense of beauty, a tendency to imitation, and the
love of excitement or novelty, could hardly fail to lead to capricious
changes of customs and fashions. I have alluded to this point, because a
recent writer (73. 'The Spectator,' Dec. 4th, 1869, p. 1430.) has oddly
fixed on Caprice "as one of the most remarkable and typical differences
between savages and brutes." But not only can we partially understand how
it is that man is from various conflicting influences rendered capricious,
but that the lower animals are, as we shall hereafter see, likewise
capricious in their affections, aversions, and sense of beauty. There is
also reason to suspect that they love novelty, for its own sake.
BELIEF IN GOD--RELIGION.
There is no evidence that man was aboriginally endowed with the ennobling
belief in the existence of an Omnipotent God. On the contrary there is
ample evidence, derived not from hasty travellers, but from men who have
long resided with savages, that numerous races have existed, and still
exist, who have no idea of one or more gods, and who have no words in their
languages to express such an idea. (74. See an excellent article on this
subject by the Rev. F.W. Farrar, in the 'Anthropological Review,' Aug.
1864, p. ccxvii. For further facts see Sir J. Lubbock, 'Prehistoric
Times,' 2nd edit., 1869, p. 564; and especially the chapters on Religion in
his 'Origin of Civilisation,' 1870.) The question is of course wholly
distinct from that higher one, whether there exists a Creator and Ruler of
the universe; and this has been answered in the affirmative by some of the
highest intellects that have ever existed.
If, however, we include under the term "religion" the belief in unseen or
spiritual agencies, the case is wholly different; for this belief seems to
be universal with the less civilised races. Nor is it difficult to
comprehend how it arose. As soon as the important faculties of the
imagination, wonder, and curiosity, together with some power of reasoning,
had become partially developed, man would naturally crave to understand
what was passing around him, and would have vaguely speculated on his own
existence. As Mr. M'Lennan (75. 'The Worship of Animals and Plants,' in
the 'Fortnightly Review,' Oct. 1, 1869, p. 422.) has remarked, "Some
explanation of the phenomena of life, a man must feign for himself, and to
judge from the universality of it, the simplest hypothesis, and the first
to occur to men, seems to have been that natural phenomena are ascribable
to the presence in animals, plants, and things, and in the forces of
nature, of such spirits prompting to action as men are conscious they
themselves possess." It is also probable, as Mr. Tylor has shewn, that
dreams may have first given rise to the notion of spirits; for savages do
not readily distinguish between subjective and objective impressions. When
a savage dreams, the figures which appear before him are believed to have
come from a distance, and to stand over him; or "the soul of the dreamer
goes out on its travels, and comes home with a remembrance of what it has
seen." (76. Tylor, 'Early History of Mankind,' 1865, p. 6. See also the
three striking chapters on the 'Development of Religion,' in Lubbock's
'Origin of Civilisation,' 1870. In a like manner Mr. Herbert Spencer, in
his ingenious essay in the 'Fortnightly Review' (May 1st, 1870, p. 535),
accounts for the earliest forms of religious belief throughout the world,
by man being led through dreams, shadows, and other causes, to look at
himself as a double essence, corporeal and spiritual. As the spiritual
being is supposed to exist after death and to be powerful, it is
propitiated by various gifts and ceremonies, and its aid invoked. He then
further shews that names or nicknames given from some animal or other
object, to the early progenitors or founders of a tribe, are supposed after
a long interval to represent the real progenitor of the tribe; and such
animal or object is then naturally believed still to exist as a spirit, is
held sacred, and worshipped as a god. Nevertheless I cannot but suspect
that there is a still earlier and ruder stage, when anything which
manifests power or movement is thought to be endowed with some form of
life, and with mental faculties analogous to our own.) But until the
faculties of imagination, curiosity, reason, etc., had been fairly well
developed in the mind of man, his dreams would not have led him to believe
in spirits, any more than in the case of a dog.
The tendency in savages to imagine that natural objects and agencies are
animated by spiritual or living essences, is perhaps illustrated by a
little fact which I once noticed: my dog, a full-grown and very sensible
animal, was lying on the lawn during a hot and still day; but at a little
distance a slight breeze occasionally moved an open parasol, which would
have been wholly disregarded by the dog, had any one stood near it. As it
was, every time that the parasol slightly moved, the dog growled fiercely
and barked. He must, I think, have reasoned to himself in a rapid and
unconscious manner, that movement without any apparent cause indicated the
presence of some strange living agent, and that no stranger had a right to
be on his territory.
The belief in spiritual agencies would easily pass into the belief in the
existence of one or more gods. For savages would naturally attribute to
spirits the same passions, the same love of vengeance or simplest form of
justice, and the same affections which they themselves feel. The Fuegians
appear to be in this respect in an intermediate condition, for when the
surgeon on board the "Beagle" shot some young ducklings as specimens, York
Minster declared in the most solemn manner, "Oh, Mr. Bynoe, much rain, much
snow, blow much"; and this was evidently a retributive punishment for
wasting human food. So again he related how, when his brother killed a
"wild man," storms long raged, much rain and snow fell. Yet we could never
discover that the Fuegians believed in what we should call a God, or
practised any religious rites; and Jemmy Button, with justifiable pride,
stoutly maintained that there was no devil in his land. This latter
assertion is the more remarkable, as with savages the belief in bad spirits
is far more common than that in good ones.
The feeling of religious devotion is a highly complex one, consisting of
love, complete submission to an exalted and mysterious superior, a strong
sense of dependence (77. See an able article on the 'Physical Elements of
Religion,' by Mr. L. Owen Pike, in 'Anthropological Review,' April 1870, p.
lxiii.), fear, reverence, gratitude, hope for the future, and perhaps other
elements. No being could experience so complex an emotion until advanced
in his intellectual and moral faculties to at least a moderately high
level. Nevertheless, we see some distant approach to this state of mind in
the deep love of a dog for his master, associated with complete submission,
some fear, and perhaps other feelings. The behaviour of a dog when
returning to his master after an absence, and, as I may add, of a monkey to
his beloved keeper, is widely different from that towards their fellows.
In the latter case the transports of joy appear to be somewhat less, and
the sense of equality is shewn in every action. Professor Braubach goes so
far as to maintain that a dog looks on his master as on a god. (78.
'Religion, Moral, etc., der Darwin'schen Art-Lehre,' 1869, s. 53. It is
said (Dr. W. Lauder Lindsay, 'Journal of Mental Science,' 1871, p. 43),
that Bacon long ago, and the poet Burns, held the same notion.)
The same high mental faculties which first led man to believe in unseen
spiritual agencies, then in fetishism, polytheism, and ultimately in
monotheism, would infallibly lead him, as long as his reasoning powers
remained poorly developed, to various strange superstitions and customs.
Many of these are terrible to think of--such as the sacrifice of human
beings to a blood-loving god; the trial of innocent persons by the ordeal
of poison or fire; witchcraft, etc.--yet it is well occasionally to reflect
on these superstitions, for they shew us what an infinite debt of gratitude
we owe to the improvement of our reason, to science, and to our accumulated
knowledge. As Sir J. Lubbock (79. 'Prehistoric Times,' 2nd edit., p. 571.
In this work (p. 571) there will be found an excellent account of the many
strange and capricious customs of savages.) has well observed, "it is not
too much to say that the horrible dread of unknown evil hangs like a thick
cloud over savage life, and embitters every pleasure." These miserable and
indirect consequences of our highest faculties may be compared with the
incidental and occasional mistakes of the instincts of the lower animals.
CHAPTER IV.
COMPARISON OF THE MENTAL POWERS OF MAN AND THE LOWER ANIMALS--continued.
The moral sense--Fundamental proposition--The qualities of social animals--
Origin of sociability--Struggle between opposed instincts--Man a social
animal--The more enduring social instincts conquer other less persistent
instincts--The social virtues alone regarded by savages--The self-regarding
virtues acquired at a later stage of development--The importance of the
judgment of the members of the same community on conduct--Transmission of
moral tendencies--Summary.
I fully subscribe to the judgment of those writers (1. See, for instance,
on this subject, Quatrefages, 'Unite de l'Espece Humaine,' 1861, p. 21,
etc.) who maintain that of all the differences between man and the lower
animals, the moral sense or conscience is by far the most important. This
sense, as Mackintosh (2. 'Dissertation an Ethical Philosophy,' 1837, p.
231, etc.) remarks, "has a rightful supremacy over every other principle of
human action"; it is summed up in that short but imperious word "ought," so
full of high significance. It is the most noble of all the attributes of
man, leading him without a moment's hesitation to risk his life for that of
a fellow-creature; or after due deliberation, impelled simply by the deep
feeling of right or duty, to sacrifice it in some great cause. Immanuel
Kant exclaims, "Duty! Wondrous thought, that workest neither by fond
insinuation, flattery, nor by any threat, but merely by holding up thy
naked law in the soul, and so extorting for thyself always reverence, if
not always obedience; before whom all appetites are dumb, however secretly
they rebel; whence thy original?" (3. 'Metaphysics of Ethics,' translated
by J.W. Semple, Edinburgh, 1836, p. 136.)
This great question has been discussed by many writers (4. Mr. Bain gives
a list ('Mental and Moral Science,' 1868, pp. 543-725) of twenty-six
British authors who have written on this subject, and whose names are
familiar to every reader; to these, Mr. Bain's own name, and those of Mr.
Lecky, Mr. Shadworth Hodgson, Sir J. Lubbock, and others, might be added.)
of consummate ability; and my sole excuse for touching on it, is the
impossibility of here passing it over; and because, as far as I know, no
one has approached it exclusively from the side of natural history. The
investigation possesses, also, some independent interest, as an attempt to
see how far the study of the lower animals throws light on one of the
highest psychical faculties of man.
The following proposition seems to me in a high degree probable--namely,
that any animal whatever, endowed with well-marked social instincts (5.
Sir B. Brodie, after observing that man is a social animal ('Psychological
Enquiries,' 1854, p. 192), asks the pregnant question, "ought not this to
settle the disputed question as to the existence of a moral sense?"
Similar ideas have probably occurred to many persons, as they did long ago
to Marcus Aurelius. Mr. J.S. Mill speaks, in his celebrated work,
'Utilitarianism,' (1864, pp. 45, 46), of the social feelings as a "powerful
natural sentiment," and as "the natural basis of sentiment for utilitarian
morality." Again he says, "Like the other acquired capacities above
referred to, the moral faculty, if not a part of our nature, is a natural
out-growth from it; capable, like them, in a certain small degree of
springing up spontaneously." But in opposition to all this, he also
remarks, "if, as in my own belief, the moral feelings are not innate, but
acquired, they are not for that reason less natural." It is with
hesitation that I venture to differ at all from so profound a thinker, but
it can hardly be disputed that the social feelings are instinctive or
innate in the lower animals; and why should they not be so in man? Mr.
Bain (see, for instance, 'The Emotions and the Will,' 1865, p. 481) and
others believe that the moral sense is acquired by each individual during
his lifetime. On the general theory of evolution this is at least
extremely improbable. The ignoring of all transmitted mental qualities
will, as it seems to me, be hereafter judged as a most serious blemish in
the works of Mr. Mill.), the parental and filial affections being here
included, would inevitably acquire a moral sense or conscience, as soon as
its intellectual powers had become as well, or nearly as well developed, as
in man. For, FIRSTLY, the social instincts lead an animal to take pleasure
in the society of its fellows, to feel a certain amount of sympathy with
them, and to perform various services for them. The services may be of a
definite and evidently instinctive nature; or there may be only a wish and
readiness, as with most of the higher social animals, to aid their fellows
in certain general ways. But these feelings and services are by no means
extended to all the individuals of the same species, only to those of the
same association. SECONDLY, as soon as the mental faculties had become
highly developed, images of all past actions and motives would be
incessantly passing through the brain of each individual: and that feeling
of dissatisfaction, or even misery, which invariably results, as we shall
hereafter see, from any unsatisfied instinct, would arise, as often as it
was perceived that the enduring and always present social instinct had
yielded to some other instinct, at the time stronger, but neither enduring
in its nature, nor leaving behind it a very vivid impression. It is clear
that many instinctive desires, such as that of hunger, are in their nature
of short duration; and after being satisfied, are not readily or vividly
recalled. THIRDLY, after the power of language had been acquired, and the
wishes of the community could be expressed, the common opinion how each
member ought to act for the public good, would naturally become in a
paramount degree the guide to action. But it should be borne in mind that
however great weight we may attribute to public opinion, our regard for the
approbation and disapprobation of our fellows depends on sympathy, which,
as we shall see, forms an essential part of the social instinct, and is
indeed its foundation-stone. LASTLY, habit in the individual would
ultimately play a very important part in guiding the conduct of each
member; for the social instinct, together with sympathy, is, like any other
instinct, greatly strengthened by habit, and so consequently would be
obedience to the wishes and judgment of the community. These several
subordinate propositions must now be discussed, and some of them at
considerable length.
It may be well first to premise that I do not wish to maintain that any
strictly social animal, if its intellectual faculties were to become as
active and as highly developed as in man, would acquire exactly the same
moral sense as ours. In the same manner as various animals have some sense
of beauty, though they admire widely-different objects, so they might have
a sense of right and wrong, though led by it to follow widely different
lines of conduct. If, for instance, to take an extreme case, men were
reared under precisely the same conditions as hive-bees, there can hardly
be a doubt that our unmarried females would, like the worker-bees, think it
a sacred duty to kill their brothers, and mothers would strive to kill
their fertile daughters; and no one would think of interfering. (6. Mr.
H. Sidgwick remarks, in an able discussion on this subject (the 'Academy,'
June 15, 1872, p. 231), "a superior bee, we may feel sure, would aspire to
a milder solution of the population question." Judging, however, from the
habits of many or most savages, man solves the problem by female
infanticide, polyandry and promiscuous intercourse; therefore it may well
be doubted whether it would be by a milder method. Miss Cobbe, in
commenting ('Darwinism in Morals,' 'Theological Review,' April 1872, pp.
188-191) on the same illustration, says, the PRINCIPLES of social duty
would be thus reversed; and by this, I presume, she means that the
fulfilment of a social duty would tend to the injury of individuals; but
she overlooks the fact, which she would doubtless admit, that the instincts
of the bee have been acquired for the good of the community. She goes so
far as to say that if the theory of ethics advocated in this chapter were
ever generally accepted, "I cannot but believe that in the hour of their
triumph would be sounded the knell of the virtue of mankind!" It is to be
hoped that the belief in the permanence of virtue on this earth is not held
by many persons on so weak a tenure.) Nevertheless, the bee, or any other
social animal, would gain in our supposed case, as it appears to me, some
feeling of right or wrong, or a conscience. For each individual would have
an inward sense of possessing certain stronger or more enduring instincts,
and others less strong or enduring; so that there would often be a struggle
as to which impulse should be followed; and satisfaction, dissatisfaction,
or even misery would be felt, as past impressions were compared during
their incessant passage through the mind. In this case an inward monitor
would tell the animal that it would have been better to have followed the
one impulse rather than the other. The one course ought to have been
followed, and the other ought not; the one would have been right and the
other wrong; but to these terms I shall recur.
SOCIABILITY.
Animals of many kinds are social; we find even distinct species living
together; for example, some American monkeys; and united flocks of rooks,
jackdaws, and starlings. Man shews the same feeling in his strong love for
the dog, which the dog returns with interest. Every one must have noticed
how miserable horses, dogs, sheep, etc., are when separated from their
companions, and what strong mutual affection the two former kinds, at
least, shew on their reunion. It is curious to speculate on the feelings
of a dog, who will rest peacefully for hours in a room with his master or
any of the family, without the least notice being taken of him; but if left
for a short time by himself, barks or howls dismally. We will confine our
attention to the higher social animals; and pass over insects, although
some of these are social, and aid one another in many important ways. The
most common mutual service in the higher animals is to warn one another of
danger by means of the united senses of all. Every sportsman knows, as Dr.
Jaeger remarks (7. 'Die Darwin'sche Theorie,' s. 101.), how difficult it
is to approach animals in a herd or troop. Wild horses and cattle do not,
I believe, make any danger-signal; but the attitude of any one of them who
first discovers an enemy, warns the others. Rabbits stamp loudly on the
ground with their hind-feet as a signal: sheep and chamois do the same
with their forefeet, uttering likewise a whistle. Many birds, and some
mammals, post sentinels, which in the case of seals are said (8. Mr. R.
Brown in 'Proc. Zoolog. Soc.' 1868, p. 409.) generally to be the females.
The leader of a troop of monkeys acts as the sentinel, and utters cries
expressive both of danger and of safety. (9. Brehm, 'Thierleben,' B. i.
1864, s. 52, 79. For the case of the monkeys extracting thorns from each
other, see s. 54. With respect to the Hamadryas turning over stones, the
fact is given (s. 76), on the evidence of Alvarez, whose observations Brehm
thinks quite trustworthy. For the cases of the old male baboons attacking
the dogs, see s. 79; and with respect to the eagle, s. 56.) Social animals
perform many little services for each other: horses nibble, and cows lick
each other, on any spot which itches: monkeys search each other for
external parasites; and Brehm states that after a troop of the
Cercopithecus griseo-viridis has rushed through a thorny brake, each monkey
stretches itself on a branch, and another monkey sitting by,
"conscientiously" examines its fur, and extracts every thorn or burr.
Animals also render more important services to one another: thus wolves
and some other beasts of prey hunt in packs, and aid one another in
attacking their victims. Pelicans fish in concert. The Hamadryas baboons
turn over stones to find insects, etc.; and when they come to a large one,
as many as can stand round, turn it over together and share the booty.
Social animals mutually defend each other. Bull bisons in N. America, when
there is danger, drive the cows and calves into the middle of the herd,
whilst they defend the outside. I shall also in a future chapter give an
account of two young wild bulls at Chillingham attacking an old one in
concert, and of two stallions together trying to drive away a third
stallion from a troop of mares. In Abyssinia, Brehm encountered a great
troop of baboons who were crossing a valley: some had already ascended the
opposite mountain, and some were still in the valley; the latter were
attacked by the dogs, but the old males immediately hurried down from the
rocks, and with mouths widely opened, roared so fearfully, that the dogs
quickly drew back. They were again encouraged to the attack; but by this
time all the baboons had reascended the heights, excepting a young one,
about six months old, who, loudly calling for aid, climbed on a block of
rock, and was surrounded. Now one of the largest males, a true hero, came
down again from the mountain, slowly went to the young one, coaxed him, and
triumphantly led him away--the dogs being too much astonished to make an
attack. I cannot resist giving another scene which was witnessed by this
same naturalist; an eagle seized a young Cercopithecus, which, by clinging
to a branch, was not at once carried off; it cried loudly for assistance,
upon which the other members of the troop, with much uproar, rushed to the
rescue, surrounded the eagle, and pulled out so many feathers, that he no
longer thought of his prey, but only how to escape. This eagle, as Brehm
remarks, assuredly would never again attack a single monkey of a troop.
(10. Mr. Belt gives the case of a spider-monkey (Ateles) in Nicaragua,
which was heard screaming for nearly two hours in the forest, and was found
with an eagle perched close by it. The bird apparently feared to attack as
long as it remained face to face; and Mr. Belt believes, from what he has
seen of the habits of these monkeys, that they protect themselves from
eagles by keeping two or three together. 'The Naturalist in Nicaragua,'
1874, p. 118.)
It is certain that associated animals have a feeling of love for each
other, which is not felt by non-social adult animals. How far in most
cases they actually sympathise in the pains and pleasures of others, is
more doubtful, especially with respect to pleasures. Mr. Buxton, however,
who had excellent means of observation (11. 'Annals and Magazine of
Natural History,' November 1868, p. 382.), states that his macaws, which
lived free in Norfolk, took "an extravagant interest" in a pair with a
nest; and whenever the female left it, she was surrounded by a troop
"screaming horrible acclamations in her honour." It is often difficult to
judge whether animals have any feeling for the sufferings of others of
their kind. Who can say what cows feel, when they surround and stare
intently on a dying or dead companion; apparently, however, as Houzeau
remarks, they feel no pity. That animals sometimes are far from feeling
any sympathy is too certain; for they will expel a wounded animal from the
herd, or gore or worry it to death. This is almost the blackest fact in
natural history, unless, indeed, the explanation which has been suggested
is true, that their instinct or reason leads them to expel an injured
companion, lest beasts of prey, including man, should be tempted to follow
the troop. In this case their conduct is not much worse than that of the
North American Indians, who leave their feeble comrades to perish on the
plains; or the Fijians, who, when their parents get old, or fall ill, bury
them alive. (12. Sir J. Lubbock, 'Prehistoric Times,' 2nd ed., p. 446.)
Many animals, however, certainly sympathise with each other's distress or
danger. This is the case even with birds. Captain Stansbury (13. As
quoted by Mr. L.H. Morgan, 'The American Beaver,' 1868, p. 272. Capt.
Stansbury also gives an interesting account of the manner in which a very
young pelican, carried away by a strong stream, was guided and encouraged
in its attempts to reach the shore by half a dozen old birds.) found on a
salt lake in Utah an old and completely blind pelican, which was very fat,
and must have been well fed for a long time by his companions. Mr. Blyth,
as he informs me, saw Indian crows feeding two or three of their companions
which were blind; and I have heard of an analogous case with the domestic
cock. We may, if we choose, call these actions instinctive; but such cases
are much too rare for the development of any special instinct. (14. As
Mr. Bain states, "effective aid to a sufferer springs from sympathy
proper:" 'Mental and Moral Science,' 1868, p. 245.) I have myself seen a
dog, who never passed a cat who lay sick in a basket, and was a great
friend of his, without giving her a few licks with his tongue, the surest
sign of kind feeling in a dog.
It must be called sympathy that leads a courageous dog to fly at any one
who strikes his master, as he certainly will. I saw a person pretending to
beat a lady, who had a very timid little dog on her lap, and the trial had
never been made before; the little creature instantly jumped away, but
after the pretended beating was over, it was really pathetic to see how
perseveringly he tried to lick his mistress's face, and comfort her. Brehm
(15. 'Thierleben,' B. i. s. 85.) states that when a baboon in confinement
was pursued to be punished, the others tried to protect him. It must have
been sympathy in the cases above given which led the baboons and
Cercopitheci to defend their young comrades from the dogs and the eagle. I
will give only one other instance of sympathetic and heroic conduct, in the
case of a little American monkey. Several years ago a keeper at the
Zoological Gardens shewed me some deep and scarcely healed wounds on the
nape of his own neck, inflicted on him, whilst kneeling on the floor, by a
fierce baboon. The little American monkey, who was a warm friend of this
keeper, lived in the same large compartment, and was dreadfully afraid of
the great baboon. Nevertheless, as soon as he saw his friend in peril, he
rushed to the rescue, and by screams and bites so distracted the baboon
that the man was able to escape, after, as the surgeon thought, running
great risk of his life.
Besides love and sympathy, animals exhibit other qualities connected with
the social instincts, which in us would be called moral; and I agree with
Agassiz (16. 'De l'Espece et de la Classe,' 1869, p. 97.) that dogs
possess something very like a conscience.
Dogs possess some power of self-command, and this does not appear to be
wholly the result of fear. As Braubach (17. 'Die Darwin'sche Art-Lehre,'
1869, s. 54.) remarks, they will refrain from stealing food in the absence
of their master. They have long been accepted as the very type of fidelity
and obedience. But the elephant is likewise very faithful to his driver or
keeper, and probably considers him as the leader of the herd. Dr. Hooker
informs me that an elephant, which he was riding in India, became so deeply
bogged that he remained stuck fast until the next day, when he was
extricated by men with ropes. Under such circumstances elephants will
seize with their trunks any object, dead or alive, to place under their
knees, to prevent their sinking deeper in the mud; and the driver was
dreadfully afraid lest the animal should have seized Dr. Hooker and crushed
him to death. But the driver himself, as Dr. Hooker was assured, ran no
risk. This forbearance under an emergency so dreadful for a heavy animal,
is a wonderful proof of noble fidelity. (18. See also Hooker's 'Himalayan
Journals,' vol. ii. 1854, p. 333.)
All animals living in a body, which defend themselves or attack their
enemies in concert, must indeed be in some degree faithful to one another;
and those that follow a leader must be in some degree obedient. When the
baboons in Abyssinia (19. Brehm, 'Thierleben,' B. i. s. 76.) plunder a
garden, they silently follow their leader; and if an imprudent young animal
makes a noise, he receives a slap from the others to teach him silence and
obedience. Mr. Galton, who has had excellent opportunities for observing
the half-wild cattle in S. Africa, says (20. See his extremely interesting
paper on 'Gregariousness in Cattle, and in Man,' 'Macmillan's Magazine,'
Feb. 1871, p. 353.), that they cannot endure even a momentary separation
from the herd. They are essentially slavish, and accept the common
determination, seeking no better lot than to be led by any one ox who has
enough self-reliance to accept the position. The men who break in these
animals for harness, watch assiduously for those who, by grazing apart,
shew a self-reliant disposition, and these they train as fore-oxen. Mr.
Galton adds that such animals are rare and valuable; and if many were born
they would soon be eliminated, as lions are always on the look-out for the
individuals which wander from the herd.
With respect to the impulse which leads certain animals to associate
together, and to aid one another in many ways, we may infer that in most
cases they are impelled by the same sense of satisfaction or pleasure which
they experience in performing other instinctive actions; or by the same
sense of dissatisfaction as when other instinctive actions are checked. We
see this in innumerable instances, and it is illustrated in a striking
manner by the acquired instincts of our domesticated animals; thus a young
shepherd-dog delights in driving and running round a flock of sheep, but
not in worrying them; a young fox-hound delights in hunting a fox, whilst
some other kinds of dogs, as I have witnessed, utterly disregard foxes.
What a strong feeling of inward satisfaction must impel a bird, so full of
activity, to brood day after day over her eggs. Migratory birds are quite
miserable if stopped from migrating; perhaps they enjoy starting on their
long flight; but it is hard to believe that the poor pinioned goose,
described by Audubon, which started on foot at the proper time for its
journey of probably more than a thousand miles, could have felt any joy in
doing so. Some instincts are determined solely by painful feelings, as by
fear, which leads to self-preservation, and is in some cases directed
towards special enemies. No one, I presume, can analyse the sensations of
pleasure or pain. In many instances, however, it is probable that
instincts are persistently followed from the mere force of inheritance,
without the stimulus of either pleasure or pain. A young pointer, when it
first scents game, apparently cannot help pointing. A squirrel in a cage
who pats the nuts which it cannot eat, as if to bury them in the ground,
can hardly be thought to act thus, either from pleasure or pain. Hence the
common assumption that men must be impelled to every action by experiencing
some pleasure or pain may be erroneous. Although a habit may be blindly
and implicitly followed, independently of any pleasure or pain felt at the
moment, yet if it be forcibly and abruptly checked, a vague sense of
dissatisfaction is generally experienced.
It has often been assumed that animals were in the first place rendered
social, and that they feel as a consequence uncomfortable when separated
from each other, and comfortable whilst together; but it is a more probable
view that these sensations were first developed, in order that those
animals which would profit by living in society, should be induced to live
together, in the same manner as the sense of hunger and the pleasure of
eating were, no doubt, first acquired in order to induce animals to eat.
The feeling of pleasure from society is probably an extension of the
parental or filial affections, since the social instinct seems to be
developed by the young remaining for a long time with their parents; and
this extension may be attributed in part to habit, but chiefly to natural
selection. With those animals which were benefited by living in close
association, the individuals which took the greatest pleasure in society
would best escape various dangers, whilst those that cared least for their
comrades, and lived solitary, would perish in greater numbers. With
respect to the origin of the parental and filial affections, which
apparently lie at the base of the social instincts, we know not the steps
by which they have been gained; but we may infer that it has been to a
large extent through natural selection. So it has almost certainly been
with the unusual and opposite feeling of hatred between the nearest
relations, as with the worker-bees which kill their brother drones, and
with the queen-bees which kill their daughter-queens; the desire to destroy
their nearest relations having been in this case of service to the
community. Parental affection, or some feeling which replaces it, has been
developed in certain animals extremely low in the scale, for example, in
star-fishes and spiders. It is also occasionally present in a few members
alone in a whole group of animals, as in the genus Forficula, or earwigs.
The all-important emotion of sympathy is distinct from that of love. A
mother may passionately love her sleeping and passive infant, but she can
hardly at such times be said to feel sympathy for it. The love of a man
for his dog is distinct from sympathy, and so is that of a dog for his
master. Adam Smith formerly argued, as has Mr. Bain recently, that the
basis of sympathy lies in our strong retentiveness of former states of pain
or pleasure. Hence, "the sight of another person enduring hunger, cold,
fatigue, revives in us some recollection of these states, which are painful
even in idea." We are thus impelled to relieve the sufferings of another,
in order that our own painful feelings may be at the same time relieved.
In like manner we are led to participate in the pleasures of others. (21.
See the first and striking chapter in Adam Smith's 'Theory of Moral
Sentiments.' Also 'Mr. Bain's Mental and Moral Science,' 1868, pp. 244,
and 275-282. Mr. Bain states, that, "sympathy is, indirectly, a source of
pleasure to the sympathiser"; and he accounts for this through reciprocity.
He remarks that "the person benefited, or others in his stead, may make up,
by sympathy and good offices returned, for all the sacrifice." But if, as
appears to be the case, sympathy is strictly an instinct, its exercise
would give direct pleasure, in the same manner as the exercise, as before
remarked, of almost every other instinct.) But I cannot see how this view
explains the fact that sympathy is excited, in an immeasurably stronger
degree, by a beloved, than by an indifferent person. The mere sight of
suffering, independently of love, would suffice to call up in us vivid
recollections and associations. The explanation may lie in the fact that,
with all animals, sympathy is directed solely towards the members of the
same community, and therefore towards known, and more or less beloved
members, but not to all the individuals of the same species. This fact is
not more surprising than that the fears of many animals should be directed
against special enemies. Species which are not social, such as lions and
tigers, no doubt feel sympathy for the suffering of their own young, but
not for that of any other animal. With mankind, selfishness, experience,
and imitation, probably add, as Mr. Bain has shewn, to the power of
sympathy; for we are led by the hope of receiving good in return to perform
acts of sympathetic kindness to others; and sympathy is much strengthened
by habit. In however complex a manner this feeling may have originated, as
it is one of high importance to all those animals which aid and defend one
another, it will have been increased through natural selection; for those
communities, which included the greatest number of the most sympathetic
members, would flourish best, and rear the greatest number of offspring.
It is, however, impossible to decide in many cases whether certain social
instincts have been acquired through natural selection, or are the indirect
result of other instincts and faculties, such as sympathy, reason,
experience, and a tendency to imitation; or again, whether they are simply
the result of long-continued habit. So remarkable an instinct as the
placing sentinels to warn the community of danger, can hardly have been the
indirect result of any of these faculties; it must, therefore, have been
directly acquired. On the other hand, the habit followed by the males of
some social animals of defending the community, and of attacking their
enemies or their prey in concert, may perhaps have originated from mutual
sympathy; but courage, and in most cases strength, must have been
previously acquired, probably through natural selection.
Of the various instincts and habits, some are much stronger than others;
that is, some either give more pleasure in their performance, and more
distress in their prevention, than others; or, which is probably quite as
important, they are, through inheritance, more persistently followed,
without exciting any special feeling of pleasure or pain. We are ourselves
conscious that some habits are much more difficult to cure or change than
others. Hence a struggle may often be observed in animals between
different instincts, or between an instinct and some habitual disposition;
as when a dog rushes after a hare, is rebuked, pauses, hesitates, pursues
again, or returns ashamed to his master; or as between the love of a female
dog for her young puppies and for her master,--for she may be seen to slink
away to them, as if half ashamed of not accompanying her master. But the
most curious instance known to me of one instinct getting the better of
another, is the migratory instinct conquering the maternal instinct. The
former is wonderfully strong; a confined bird will at the proper season
beat her breast against the wires of her cage, until it is bare and bloody.
It causes young salmon to leap out of the fresh water, in which they could
continue to exist, and thus unintentionally to commit suicide. Every one
knows how strong the maternal instinct is, leading even timid birds to face
great danger, though with hesitation, and in opposition to the instinct of
self-preservation. Nevertheless, the migratory instinct is so powerful,
that late in the autumn swallows, house-martins, and swifts frequently
desert their tender young, leaving them to perish miserably in their nests.
(22. This fact, the Rev. L. Jenyns states (see his edition of 'White's
Nat. Hist. of Selborne,' 1853, p. 204) was first recorded by the
illustrious Jenner, in 'Phil. Transact.' 1824, and has since been confirmed
by several observers, especially by Mr. Blackwall. This latter careful
observer examined, late in the autumn, during two years, thirty-six nests;
he found that twelve contained young dead birds, five contained eggs on the
point of being hatched, and three, eggs not nearly hatched. Many birds,
not yet old enough for a prolonged flight, are likewise deserted and left
behind. See Blackwall, 'Researches in Zoology,' 1834, pp. 108, 118. For
some additional evidence, although this is not wanted, see Leroy, 'Lettres
Phil.' 1802, p. 217. For Swifts, Gould's 'Introduction to the Birds of
Great Britain,' 1823, p. 5. Similar cases have been observed in Canada by
Mr. Adams; 'Pop. Science Review,' July 1873, p. 283.)
We can perceive that an instinctive impulse, if it be in any way more
beneficial to a species than some other or opposed instinct, would be
rendered the more potent of the two through natural selection; for the
individuals which had it most strongly developed would survive in larger
numbers. Whether this is the case with the migratory in comparison with
the maternal instinct, may be doubted. The great persistence, or steady
action of the former at certain seasons of the year during the whole day,
may give it for a time paramount force.
MAN A SOCIAL ANIMAL.
Every one will admit that man is a social being. We see this in his
dislike of solitude, and in his wish for society beyond that of his own
family. Solitary confinement is one of the severest punishments which can
be inflicted. Some authors suppose that man primevally lived in single
families; but at the present day, though single families, or only two or
three together, roam the solitudes of some savage lands, they always, as
far as I can discover, hold friendly relations with other families
inhabiting the same district. Such families occasionally meet in council,
and unite for their common defence. It is no argument against savage man
being a social animal, that the tribes inhabiting adjacent districts are
almost always at war with each other; for the social instincts never extend
to all the individuals of the same species. Judging from the analogy of
the majority of the Quadrumana, it is probable that the early ape-like
progenitors of man were likewise social; but this is not of much importance
for us. Although man, as he now exists, has few special instincts, having
lost any which his early progenitors may have possessed, this is no reason
why he should not have retained from an extremely remote period some degree
of instinctive love and sympathy for his fellows. We are indeed all
conscious that we do possess such sympathetic feelings (23. Hume remarks
('An Enquiry Concerning the Principles of Morals,' edit. of 1751, p. 132),
"There seems a necessity for confessing that the happiness and misery of
others are not spectacles altogether indifferent to us, but that the view
of the former...communicates a secret joy; the appearance of the latter...
throws a melancholy damp over the imagination."); but our consciousness
does not tell us whether they are instinctive, having originated long ago
in the same manner as with the lower animals, or whether they have been
acquired by each of us during our early years. As man is a social animal,
it is almost certain that he would inherit a tendency to be faithful to his
comrades, and obedient to the leader of his tribe; for these qualities are
common to most social animals. He would consequently possess some capacity
for self-command. He would from an inherited tendency be willing to
defend, in concert with others, his fellow-men; and would be ready to aid
them in any way, which did not too greatly interfere with his own welfare
or his own strong desires.
The social animals which stand at the bottom of the scale are guided almost
exclusively, and those which stand higher in the scale are largely guided,
by special instincts in the aid which they give to the members of the same
community; but they are likewise in part impelled by mutual love and
sympathy, assisted apparently by some amount of reason. Although man, as
just remarked, has no special instincts to tell him how to aid his fellow-
men, he still has the impulse, and with his improved intellectual faculties
would naturally be much guided in this respect by reason and experience.
Instinctive sympathy would also cause him to value highly the approbation
of his fellows; for, as Mr. Bain has clearly shewn (24. 'Mental and Moral
Science,' 1868, p. 254.), the love of praise and the strong feeling of
glory, and the still stronger horror of scorn and infamy, "are due to the
workings of sympathy." Consequently man would be influenced in the highest
degree by the wishes, approbation, and blame of his fellow-men, as
expressed by their gestures and language. Thus the social instincts, which
must have been acquired by man in a very rude state, and probably even by
his early ape-like progenitors, still give the impulse to some of his best
actions; but his actions are in a higher degree determined by the expressed
wishes and judgment of his fellow-men, and unfortunately very often by his
own strong selfish desires. But as love, sympathy and self-command become
strengthened by habit, and as the power of reasoning becomes clearer, so
that man can value justly the judgments of his fellows, he will feel
himself impelled, apart from any transitory pleasure or pain, to certain
lines of conduct. He might then declare--not that any barbarian or
uncultivated man could thus think--I am the supreme judge of my own
conduct, and in the words of Kant, I will not in my own person violate the
dignity of humanity.
THE MORE ENDURING SOCIAL INSTINCTS CONQUER THE LESS PERSISTENT INSTINCTS.
We have not, however, as yet considered the main point, on which, from our
present point of view, the whole question of the moral sense turns. Why
should a man feel that he ought to obey one instinctive desire rather than
another? Why is he bitterly regretful, if he has yielded to a strong sense
of self-preservation, and has not risked his life to save that of a fellow-
creature? or why does he regret having stolen food from hunger?
It is evident in the first place, that with mankind the instinctive
impulses have different degrees of strength; a savage will risk his own
life to save that of a member of the same community, but will be wholly
indifferent about a stranger: a young and timid mother urged by the
maternal instinct will, without a moment's hesitation, run the greatest
danger for her own infant, but not for a mere fellow-creature.
Nevertheless many a civilised man, or even boy, who never before risked his
life for another, but full of courage and sympathy, has disregarded the
instinct of self-preservation, and plunged at once into a torrent to save a
drowning man, though a stranger. In this case man is impelled by the same
instinctive motive, which made the heroic little American monkey, formerly
described, save his keeper, by attacking the great and dreaded baboon.
Such actions as the above appear to be the simple result of the greater
strength of the social or maternal instincts rather than that of any other
instinct or motive; for they are performed too instantaneously for
reflection, or for pleasure or pain to be felt at the time; though, if
prevented by any cause, distress or even misery might be felt. In a timid
man, on the other hand, the instinct of self-preservation might be so
strong, that he would be unable to force himself to run any such risk,
perhaps not even for his own child.
I am aware that some persons maintain that actions performed impulsively,
as in the above cases, do not come under the dominion of the moral sense,
and cannot be called moral. They confine this term to actions done
deliberately, after a victory over opposing desires, or when prompted by
some exalted motive. But it appears scarcely possible to draw any clear
line of distinction of this kind. (25. I refer here to the distinction
between what has been called MATERIAL and FORMAL morality. I am glad to
find that Professor Huxley ('Critiques and Addresses,' 1873, p. 287) takes
the same view on this subject as I do. Mr. Leslie Stephen remarks ('Essays
on Freethinking and Plain Speaking,' 1873, p. 83), "the metaphysical
distinction, between material and formal morality is as irrelevant as other
such distinctions.") As far as exalted motives are concerned, many
instances have been recorded of savages, destitute of any feeling of
general benevolence towards mankind, and not guided by any religious
motive, who have deliberately sacrificed their lives as prisoners(26. I
have given one such case, namely of three Patagonian Indians who preferred
being shot, one after the other, to betraying the plans of their companions
in war ('Journal of Researches,' 1845, p. 103).), rather than betray their
comrades; and surely their conduct ought to be considered as moral. As far
as deliberation, and the victory over opposing motives are concerned,
animals may be seen doubting between opposed instincts, in rescuing their
offspring or comrades from danger; yet their actions, though done for the
good of others, are not called moral. Moreover, anything performed very
often by us, will at last be done without deliberation or hesitation, and
can then hardly be distinguished from an instinct; yet surely no one will
pretend that such an action ceases to be moral. On the contrary, we all
feel that an act cannot be considered as perfect, or as performed in the
most noble manner, unless it be done impulsively, without deliberation or
effort, in the same manner as by a man in whom the requisite qualities are
innate. He who is forced to overcome his fear or want of sympathy before
he acts, deserves, however, in one way higher credit than the man whose
innate disposition leads him to a good act without effort. As we cannot
distinguish between motives, we rank all actions of a certain class as
moral, if performed by a moral being. A moral being is one who is capable
of comparing his past and future actions or motives, and of approving or
disapproving of them. We have no reason to suppose that any of the lower
animals have this capacity; therefore, when a Newfoundland dog drags a
child out of the water, or a monkey faces danger to rescue its comrade, or
takes charge of an orphan monkey, we do not call its conduct moral. But in
the case of man, who alone can with certainty be ranked as a moral being,
actions of a certain class are called moral, whether performed
deliberately, after a struggle with opposing motives, or impulsively
through instinct, or from the effects of slowly-gained habit.
But to return to our more immediate subject. Although some instincts are
more powerful than others, and thus lead to corresponding actions, yet it
is untenable, that in man the social instincts (including the love of
praise and fear of blame) possess greater strength, or have, through long
habit, acquired greater strength than the instincts of self-preservation,
hunger, lust, vengeance, etc. Why then does man regret, even though trying
to banish such regret, that he has followed the one natural impulse rather
than the other; and why does he further feel that he ought to regret his
conduct? Man in this respect differs profoundly from the lower animals.
Nevertheless we can, I think, see with some degree of clearness the reason
of this difference.
Man, from the activity of his mental faculties, cannot avoid reflection:
past impressions and images are incessantly and clearly passing through his
mind. Now with those animals which live permanently in a body, the social
instincts are ever present and persistent. Such animals are always ready
to utter the danger-signal, to defend the community, and to give aid to
their fellows in accordance with their habits; they feel at all times,
without the stimulus of any special passion or desire, some degree of love
and sympathy for them; they are unhappy if long separated from them, and
always happy to be again in their company. So it is with ourselves. Even
when we are quite alone, how often do we think with pleasure or pain of
what others think of us,--of their imagined approbation or disapprobation;
and this all follows from sympathy, a fundamental element of the social
instincts. A man who possessed no trace of such instincts would be an
unnatural monster. On the other hand, the desire to satisfy hunger, or any
passion such as vengeance, is in its nature temporary, and can for a time
be fully satisfied. Nor is it easy, perhaps hardly possible, to call up
with complete vividness the feeling, for instance, of hunger; nor indeed,
as has often been remarked, of any suffering. The instinct of self-
preservation is not felt except in the presence of danger; and many a
coward has thought himself brave until he has met his enemy face to face.
The wish for another man's property is perhaps as persistent a desire as
any that can be named; but even in this case the satisfaction of actual
possession is generally a weaker feeling than the desire: many a thief, if
not a habitual one, after success has wondered why he stole some article.
(27. Enmity or hatred seems also to be a highly persistent feeling, perhaps
more so than any other that can be named. Envy is defined as hatred of
another for some excellence or success; and Bacon insists (Essay ix.), "Of
all other affections envy is the most importune and continual." Dogs are
very apt to hate both strange men and strange dogs, especially if they live
near at hand, but do not belong to the same family, tribe, or clan; this
feeling would thus seem to be innate, and is certainly a most persistent
one. It seems to be the complement and converse of the true social
instinct. From what we hear of savages, it would appear that something of
the same kind holds good with them. If this be so, it would be a small
step in any one to transfer such feelings to any member of the same tribe
if he had done him an injury and had become his enemy. Nor is it probable
that the primitive conscience would reproach a man for injuring his enemy;
rather it would reproach him, if he had not revenged himself. To do good
in return for evil, to love your enemy, is a height of morality to which it
may be doubted whether the social instincts would, by themselves, have ever
led us. It is necessary that these instincts, together with sympathy,
should have been highly cultivated and extended by the aid of reason,
instruction, and the love or fear of God, before any such golden rule would
ever be thought of and obeyed.)
A man cannot prevent past impressions often repassing through his mind; he
will thus be driven to make a comparison between the impressions of past
hunger, vengeance satisfied, or danger shunned at other men's cost, with
the almost ever-present instinct of sympathy, and with his early knowledge
of what others consider as praiseworthy or blameable. This knowledge
cannot be banished from his mind, and from instinctive sympathy is esteemed
of great moment. He will then feel as if he had been baulked in following
a present instinct or habit, and this with all animals causes
dissatisfaction, or even misery.
The above case of the swallow affords an illustration, though of a reversed
nature, of a temporary though for the time strongly persistent instinct
conquering another instinct, which is usually dominant over all others. At
the proper season these birds seem all day long to be impressed with the
desire to migrate; their habits change; they become restless, are noisy and
congregate in flocks. Whilst the mother-bird is feeding, or brooding over
her nestlings, the maternal instinct is probably stronger than the
migratory; but the instinct which is the more persistent gains the victory,
and at last, at a moment when her young ones are not in sight, she takes
flight and deserts them. When arrived at the end of her long journey, and
the migratory instinct has ceased to act, what an agony of remorse the bird
would feel, if, from being endowed with great mental activity, she could
not prevent the image constantly passing through her mind, of her young
ones perishing in the bleak north from cold and hunger.
At the moment of action, man will no doubt be apt to follow the stronger
impulse; and though this may occasionally prompt him to the noblest deeds,
it will more commonly lead him to gratify his own desires at the expense of
other men. But after their gratification when past and weaker impressions
are judged by the ever-enduring social instinct, and by his deep regard for
the good opinion of his fellows, retribution will surely come. He will
then feel remorse, repentance, regret, or shame; this latter feeling,
however, relates almost exclusively to the judgment of others. He will
consequently resolve more or less firmly to act differently for the future;
and this is conscience; for conscience looks backwards, and serves as a
guide for the future.
The nature and strength of the feelings which we call regret, shame,
repentance or remorse, depend apparently not only on the strength of the
violated instinct, but partly on the strength of the temptation, and often
still more on the judgment of our fellows. How far each man values the
appreciation of others, depends on the strength of his innate or acquired
feeling of sympathy; and on his own capacity for reasoning out the remote
consequences of his acts. Another element is most important, although not
necessary, the reverence or fear of the Gods, or Spirits believed in by
each man: and this applies especially in cases of remorse. Several
critics have objected that though some slight regret or repentance may be
explained by the view advocated in this chapter, it is impossible thus to
account for the soul-shaking feeling of remorse. But I can see little
force in this objection. My critics do not define what they mean by
remorse, and I can find no definition implying more than an overwhelming
sense of repentance. Remorse seems to bear the same relation to
repentance, as rage does to anger, or agony to pain. It is far from
strange that an instinct so strong and so generally admired, as maternal
love, should, if disobeyed, lead to the deepest misery, as soon as the
impression of the past cause of disobedience is weakened. Even when an
action is opposed to no special instinct, merely to know that our friends
and equals despise us for it is enough to cause great misery. Who can
doubt that the refusal to fight a duel through fear has caused many men an
agony of shame? Many a Hindoo, it is said, has been stirred to the bottom
of his soul by having partaken of unclean food. Here is another case of
what must, I think, be called remorse. Dr. Landor acted as a magistrate in
West Australia, and relates (28. 'Insanity in Relation to Law,' Ontario,
United States, 1871, p. 1.), that a native on his farm, after losing one of
his wives from disease, came and said that, "he was going to a distant
tribe to spear a woman, to satisfy his sense of duty to his wife. I told
him that if he did so, I would send him to prison for life. He remained
about the farm for some months, but got exceedingly thin, and complained
that he could not rest or eat, that his wife's spirit was haunting him,
because he had not taken a life for hers. I was inexorable, and assured
him that nothing should save him if he did." Nevertheless the man
disappeared for more than a year, and then returned in high condition; and
his other wife told Dr. Landor that her husband had taken the life of a
woman belonging to a distant tribe; but it was impossible to obtain legal
evidence of the act. The breach of a rule held sacred by the tribe, will
thus, as it seems, give rise to the deepest feelings,--and this quite apart
from the social instincts, excepting in so far as the rule is grounded on
the judgment of the community. How so many strange superstitions have
arisen throughout the world we know not; nor can we tell how some real and
great crimes, such as incest, have come to be held in an abhorrence (which
is not however quite universal) by the lowest savages. It is even doubtful
whether in some tribes incest would be looked on with greater horror, than
would the marriage of a man with a woman bearing the same name, though not
a relation. "To violate this law is a crime which the Australians hold in
the greatest abhorrence, in this agreeing exactly with certain tribes of
North America. When the question is put in either district, is it worse to
kill a girl of a foreign tribe, or to marry a girl of one's own, an answer
just opposite to ours would be given without hesitation." (29. E.B.
Tylor, in 'Contemporary Review,' April 1873, p. 707.) We may, therefore,
reject the belief, lately insisted on by some writers, that the abhorrence
of incest is due to our possessing a special God-implanted conscience. On
the whole it is intelligible, that a man urged by so powerful a sentiment
as remorse, though arising as above explained, should be led to act in a
manner, which he has been taught to believe serves as an expiation, such as
delivering himself up to justice.
Man prompted by his conscience, will through long habit acquire such
perfect self-command, that his desires and passions will at last yield
instantly and without a struggle to his social sympathies and instincts,
including his feeling for the judgment of his fellows. The still hungry,
or the still revengeful man will not think of stealing food, or of wreaking
his vengeance. It is possible, or as we shall hereafter see, even
probable, that the habit of self-command may, like other habits, be
inherited. Thus at last man comes to feel, through acquired and perhaps
inherited habit, that it is best for him to obey his more persistent
impulses. The imperious word "ought" seems merely to imply the
consciousness of the existence of a rule of conduct, however it may have
originated. Formerly it must have been often vehemently urged that an
insulted gentleman OUGHT to fight a duel. We even say that a pointer OUGHT
to point, and a retriever to retrieve game. If they fail to do so, they
fail in their duty and act wrongly.
If any desire or instinct leading to an action opposed to the good of
others still appears, when recalled to mind, as strong as, or stronger
than, the social instinct, a man will feel no keen regret at having
followed it; but he will be conscious that if his conduct were known to his
fellows, it would meet with their disapprobation; and few are so destitute
of sympathy as not to feel discomfort when this is realised. If he has no
such sympathy, and if his desires leading to bad actions are at the time
strong, and when recalled are not over-mastered by the persistent social
instincts, and the judgment of others, then he is essentially a bad man
(30. Dr. Prosper Despine, in his Psychologie Naturelle, 1868 (tom. i. p.
243; tom. ii. p. 169) gives many curious cases of the worst criminals, who
apparently have been entirely destitute of conscience.); and the sole
restraining motive left is the fear of punishment, and the conviction that
in the long run it would be best for his own selfish interests to regard
the good of others rather than his own.
It is obvious that every one may with an easy conscience gratify his own
desires, if they do not interfere with his social instincts, that is with
the good of others; but in order to be quite free from self-reproach, or at
least of anxiety, it is almost necessary for him to avoid the
disapprobation, whether reasonable or not, of his fellow-men. Nor must he
break through the fixed habits of his life, especially if these are
supported by reason; for if he does, he will assuredly feel
dissatisfaction. He must likewise avoid the reprobation of the one God or
gods in whom, according to his knowledge or superstition, he may believe;
but in this case the additional fear of divine punishment often supervenes.
THE STRICTLY SOCIAL VIRTUES AT FIRST ALONE REGARDED.
The above view of the origin and nature of the moral sense, which tells us
what we ought to do, and of the conscience which reproves us if we disobey
it, accords well with what we see of the early and undeveloped condition of
this faculty in mankind. The virtues which must be practised, at least
generally, by rude men, so that they may associate in a body, are those
which are still recognised as the most important. But they are practised
almost exclusively in relation to the men of the same tribe; and their
opposites are not regarded as crimes in relation to the men of other
tribes. No tribe could hold together if murder, robbery, treachery, etc.,
were common; consequently such crimes within the limits of the same tribe
"are branded with everlasting infamy" (31. See an able article in the
'North British Review,' 1867, p. 395. See also Mr. W. Bagehot's articles
on the Importance of Obedience and Coherence to Primitive Man, in the
'Fortnightly Review,' 1867, p. 529, and 1868, p. 457, etc.); but excite no
such sentiment beyond these limits. A North-American Indian is well
pleased with himself, and is honoured by others, when he scalps a man of
another tribe; and a Dyak cuts off the head of an unoffending person, and
dries it as a trophy. The murder of infants has prevailed on the largest
scale throughout the world (32. The fullest account which I have met with
is by Dr. Gerland, in his 'Ueber den Aussterben der Naturvolker,' 1868; but
I shall have to recur to the subject of infanticide in a future chapter.),
and has met with no reproach; but infanticide, especially of females, has
been thought to be good for the tribe, or at least not injurious. Suicide
during former times was not generally considered as a crime (33. See the
very interesting discussion on suicide in Lecky's 'History of European
Morals,' vol. i. 1869, p. 223. With respect to savages, Mr. Winwood Reade
informs me that the negroes of West Africa often commit suicide. It is
well known how common it was amongst the miserable aborigines of South
America after the Spanish conquest. For New Zealand, see the voyage of the
"Novara," and for the Aleutian Islands, Muller, as quoted by Houzeau, 'Les
Facultes Mentales,' etc., tom. ii. p. 136.), but rather, from the courage
displayed, as an honourable act; and it is still practised by some semi-
civilised and savage nations without reproach, for it does not obviously
concern others of the tribe. It has been recorded that an Indian Thug
conscientiously regretted that he had not robbed and strangled as many
travellers as did his father before him. In a rude state of civilisation
the robbery of strangers is, indeed, generally considered as honourable.
Slavery, although in some ways beneficial during ancient times (34. See
Mr. Bagehot, 'Physics and Politics,' 1872, p. 72.), is a great crime; yet
it was not so regarded until quite recently, even by the most civilised
nations. And this was especially the case, because the slaves belonged in
general to a race different from that of their masters. As barbarians do
not regard the opinion of their women, wives are commonly treated like
slaves. Most savages are utterly indifferent to the sufferings of
strangers, or even delight in witnessing them. It is well known that the
women and children of the North-American Indians aided in torturing their
enemies. Some savages take a horrid pleasure in cruelty to animals (35.
See, for instance, Mr. Hamilton's account of the Kaffirs, 'Anthropological
Review,' 1870, p. xv.), and humanity is an unknown virtue. Nevertheless,
besides the family affections, kindness is common, especially during
sickness, between the members of the same tribe, and is sometimes extended
beyond these limits. Mungo Park's touching account of the kindness of the
negro women of the interior to him is well known. Many instances could be
given of the noble fidelity of savages towards each other, but not to
strangers; common experience justifies the maxim of the Spaniard, "Never,
never trust an Indian." There cannot be fidelity without truth; and this
fundamental virtue is not rare between the members of the same tribe: thus
Mungo Park heard the negro women teaching their young children to love the
truth. This, again, is one of the virtues which becomes so deeply rooted
in the mind, that it is sometimes practised by savages, even at a high
cost, towards strangers; but to lie to your enemy has rarely been thought a
sin, as the history of modern diplomacy too plainly shews. As soon as a
tribe has a recognised leader, disobedience becomes a crime, and even
abject submission is looked at as a sacred virtue.
As during rude times no man can be useful or faithful to his tribe without
courage, this quality has universally been placed in the highest rank; and
although in civilised countries a good yet timid man may be far more useful
to the community than a brave one, we cannot help instinctively honouring
the latter above a coward, however benevolent. Prudence, on the other
hand, which does not concern the welfare of others, though a very useful
virtue, has never been highly esteemed. As no man can practise the virtues
necessary for the welfare of his tribe without self-sacrifice, self-
command, and the power of endurance, these qualities have been at all times
highly and most justly valued. The American savage voluntarily submits to
the most horrid tortures without a groan, to prove and strengthen his
fortitude and courage; and we cannot help admiring him, or even an Indian
Fakir, who, from a foolish religious motive, swings suspended by a hook
buried in his flesh.
The other so-called self-regarding virtues, which do not obviously, though
they may really, affect the welfare of the tribe, have never been esteemed
by savages, though now highly appreciated by civilised nations. The
greatest intemperance is no reproach with savages. Utter licentiousness,
and unnatural crimes, prevail to an astounding extent. (36. Mr. M'Lennan
has given ('Primitive Marriage,' 1865, p. 176) a good collection of facts
on this head.) As soon, however, as marriage, whether polygamous, or
monogamous, becomes common, jealousy will lead to the inculcation of female
virtue; and this, being honoured, will tend to spread to the unmarried
females. How slowly it spreads to the male sex, we see at the present day.
Chastity eminently requires self-command; therefore it has been honoured
from a very early period in the moral history of civilised man. As a
consequence of this, the senseless practice of celibacy has been ranked
from a remote period as a virtue. (38. Lecky, 'History of European
Morals,' vol. i. 1869, p. 109.) The hatred of indecency, which appears to
us so natural as to be thought innate, and which is so valuable an aid to
chastity, is a modern virtue, appertaining exclusively, as Sir G. Staunton
remarks (38. 'Embassy to China,' vol. ii. p. 348.), to civilised life.
This is shewn by the ancient religious rites of various nations, by the
drawings on the walls of Pompeii, and by the practices of many savages.
We have now seen that actions are regarded by savages, and were probably so
regarded by primeval man, as good or bad, solely as they obviously affect
the welfare of the tribe,--not that of the species, nor that of an
individual member of the tribe. This conclusion agrees well with the
belief that the so-called moral sense is aboriginally derived from the
social instincts, for both relate at first exclusively to the community.
The chief causes of the low morality of savages, as judged by our standard,
are, firstly, the confinement of sympathy to the same tribe. Secondly,
powers of reasoning insufficient to recognise the bearing of many virtues,
especially of the self-regarding virtues, on the general welfare of the
tribe. Savages, for instance, fail to trace the multiplied evils
consequent on a want of temperance, chastity, etc. And, thirdly, weak
power of self-command; for this power has not been strengthened through
long-continued, perhaps inherited, habit, instruction and religion.
I have entered into the above details on the immorality of savages (39.
See on this subject copious evidence in Chap. vii. of Sir J. Lubbock,
'Origin of Civilisation,' 1870.), because some authors have recently taken
a high view of their moral nature, or have attributed most of their crimes
to mistaken benevolence. (40. For instance Lecky, 'History of European
Morals,' vol. i. p. 124.) These authors appear to rest their conclusion on
savages possessing those virtues which are serviceable, or even necessary,
for the existence of the family and of the tribe,--qualities which they
undoubtedly do possess, and often in a high degree.
CONCLUDING REMARKS.
It was assumed formerly by philosophers of the derivative (41. This term
is used in an able article in the 'Westminster Review,' Oct. 1869, p. 498.
For the "Greatest happiness principle," see J.S. Mill, 'Utilitarianism,' p.
17.) school of morals that the foundation of morality lay in a form of
Selfishness; but more recently the "Greatest happiness principle" has been
brought prominently forward. It is, however, more correct to speak of the
latter principle as the standard, and not as the motive of conduct.
Nevertheless, all the authors whose works I have consulted, with a few
exceptions (42. Mill recognises ('System of Logic,' vol. ii. p. 422) in
the clearest manner, that actions may be performed through habit without
the anticipation of pleasure. Mr. H. Sidgwick also, in his Essay on
Pleasure and Desire ('The Contemporary Review,' April 1872, p. 671),
remarks: "To sum up, in contravention of the doctrine that our conscious
active impulses are always directed towards the production of agreeable
sensations in ourselves, I would maintain that we find everywhere in
consciousness extra-regarding impulse, directed towards something that is
not pleasure; that in many cases the impulse is so far incompatible with
the self-regarding that the two do not easily co-exist in the same moment
of consciousness." A dim feeling that our impulses do not by any means
always arise from any contemporaneous or anticipated pleasure, has, I
cannot but think, been one chief cause of the acceptance of the intuitive
theory of morality, and of the rejection of the utilitarian or "Greatest
happiness" theory. With respect to the latter theory the standard and the
motive of conduct have no doubt often been confused, but they are really in
some degree blended.), write as if there must be a distinct motive for
every action, and that this must be associated with some pleasure or
displeasure. But man seems often to act impulsively, that is from instinct
or long habit, without any consciousness of pleasure, in the same manner as
does probably a bee or ant, when it blindly follows its instincts. Under
circumstances of extreme peril, as during a fire, when a man endeavours to
save a fellow-creature without a moment's hesitation, he can hardly feel
pleasure; and still less has he time to reflect on the dissatisfaction
which he might subsequently experience if he did not make the attempt.
Should he afterwards reflect over his own conduct, he would feel that there
lies within him an impulsive power widely different from a search after
pleasure or happiness; and this seems to be the deeply planted social
instinct.
In the case of the lower animals it seems much more appropriate to speak of
their social instincts, as having been developed for the general good
rather than for the general happiness of the species. The term, general
good, may be defined as the rearing of the greatest number of individuals
in full vigour and health, with all their faculties perfect, under the
conditions to which they are subjected. As the social instincts both of
man and the lower animals have no doubt been developed by nearly the same
steps, it would be advisable, if found practicable, to use the same
definition in both cases, and to take as the standard of morality, the
general good or welfare of the community, rather than the general
happiness; but this definition would perhaps require some limitation on
account of political ethics.
When a man risks his life to save that of a fellow-creature, it seems also
more correct to say that he acts for the general good, rather than for the
general happiness of mankind. No doubt the welfare and the happiness of
the individual usually coincide; and a contented, happy tribe will flourish
better than one that is discontented and unhappy. We have seen that even
at an early period in the history of man, the expressed wishes of the
community will have naturally influenced to a large extent the conduct of
each member; and as all wish for happiness, the "greatest happiness
principle" will have become a most important secondary guide and object;
the social instinct, however, together with sympathy (which leads to our
regarding the approbation and disapprobation of others), having served as
the primary impulse and guide. Thus the reproach is removed of laying the
foundation of the noblest part of our nature in the base principle of
selfishness; unless, indeed, the satisfaction which every animal feels,
when it follows its proper instincts, and the dissatisfaction felt when
prevented, be called selfish.
The wishes and opinions of the members of the same community, expressed at
first orally, but later by writing also, either form the sole guides of our
conduct, or greatly reinforce the social instincts; such opinions, however,
have sometimes a tendency directly opposed to these instincts. This latter
fact is well exemplified by the LAW OF HONOUR, that is, the law of the
opinion of our equals, and not of all our countrymen. The breach of this
law, even when the breach is known to be strictly accordant with true
morality, has caused many a man more agony than a real crime. We recognise
the same influence in the burning sense of shame which most of us have
felt, even after the interval of years, when calling to mind some
accidental breach of a trifling, though fixed, rule of etiquette. The
judgment of the community will generally be guided by some rude experience
of what is best in the long run for all the members; but this judgment will
not rarely err from ignorance and weak powers of reasoning. Hence the
strangest customs and superstitions, in complete opposition to the true
welfare and happiness of mankind, have become all-powerful throughout the
world. We see this in the horror felt by a Hindoo who breaks his caste,
and in many other such cases. It would be difficult to distinguish between
the remorse felt by a Hindoo who has yielded to the temptation of eating
unclean food, from that felt after committing a theft; but the former would
probably be the more severe.
How so many absurd rules of conduct, as well as so many absurd religious
beliefs, have originated, we do not know; nor how it is that they have
become, in all quarters of the world, so deeply impressed on the mind of
men; but it is worthy of remark that a belief constantly inculcated during
the early years of life, whilst the brain is impressible, appears to
acquire almost the nature of an instinct; and the very essence of an
instinct is that it is followed independently of reason. Neither can we
say why certain admirable virtues, such as the love of truth, are much more
highly appreciated by some savage tribes than by others (43. Good
instances are given by Mr. Wallace in 'Scientific Opinion,' Sept. 15, 1869;
and more fully in his 'Contributions to the Theory of Natural Selection,'
1870, p. 353.); nor, again, why similar differences prevail even amongst
highly civilised nations. Knowing how firmly fixed many strange customs
and superstitions have become, we need feel no surprise that the self-
regarding virtues, supported as they are by reason, should now appear to us
so natural as to be thought innate, although they were not valued by man in
his early condition.
Not withstanding many sources of doubt, man can generally and readily
distinguish between the higher and lower moral rules. The higher are
founded on the social instincts, and relate to the welfare of others. They
are supported by the approbation of our fellow-men and by reason. The
lower rules, though some of them when implying self-sacrifice hardly
deserve to be called lower, relate chiefly to self, and arise from public
opinion, matured by experience and cultivation; for they are not practised
by rude tribes.
As man advances in civilisation, and small tribes are united into larger
communities, the simplest reason would tell each individual that he ought
to extend his social instincts and sympathies to all the members of the
same nation, though personally unknown to him. This point being once
reached, there is only an artificial barrier to prevent his sympathies
extending to the men of all nations and races. If, indeed, such men are
separated from him by great differences in appearance or habits, experience
unfortunately shews us how long it is, before we look at them as our
fellow-creatures. Sympathy beyond the confines of man, that is, humanity
to the lower animals, seems to be one of the latest moral acquisitions. It
is apparently unfelt by savages, except towards their pets. How little the
old Romans knew of it is shewn by their abhorrent gladiatorial exhibitions.
The very idea of humanity, as far as I could observe, was new to most of
the Gauchos of the Pampas. This virtue, one of the noblest with which man
is endowed, seems to arise incidentally from our sympathies becoming more
tender and more widely diffused, until they are extended to all sentient
beings. As soon as this virtue is honoured and practised by some few men,
it spreads through instruction and example to the young, and eventually
becomes incorporated in public opinion.
The highest possible stage in moral culture is when we recognise that we
ought to control our thoughts, and "not even in inmost thought to think
again the sins that made the past so pleasant to us." (44. Tennyson,
Idylls of the King, p. 244.) Whatever makes any bad action familiar to the
mind, renders its performance by so much the easier. As Marcus Aurelius
long ago said, "Such as are thy habitual thoughts, such also will be the
character of thy mind; for the soul is dyed by the thoughts." (45. 'The
Thoughts of the Emperor M. Aurelius Antoninus,' English translation, 2nd
edit., 1869. p. 112. Marcus Aurelius ws born A.D. 121.)
Our great philosopher, Herbert Spencer, has recently explained his views on
the moral sense. He says (46. Letter to Mr. Mill in Bain's 'Mental and
Moral Science,' 1868, p. 722.), "I believe that the experiences of utility
organised and consolidated through all past generations of the human race,
have been producing corresponding modifications, which, by continued
transmission and accumulation, have become in us certain faculties of moral
intuition--certain emotions responding to right and wrong conduct, which
have no apparent basis in the individual experiences of utility." There is
not the least inherent improbability, as it seems to me, in virtuous
tendencies being more or less strongly inherited; for, not to mention the
various dispositions and habits transmitted by many of our domestic animals
to their offspring, I have heard of authentic cases in which a desire to
steal and a tendency to lie appeared to run in families of the upper ranks;
and as stealing is a rare crime in the wealthy classes, we can hardly
account by accidental coincidence for the tendency occurring in two or
three members of the same family. If bad tendencies are transmitted, it is
probable that good ones are likewise transmitted. That the state of the
body by affecting the brain, has great influence on the moral tendencies is
known to most of those who have suffered from chronic derangements of the
digestion or liver. The same fact is likewise shewn by the "perversion or
destruction of the moral sense being often one of the earliest symptoms of
mental derangement" (47. Maudsley, 'Body and Mind,' 1870, p. 60.); and
insanity is notoriously often inherited. Except through the principle of
the transmission of moral tendencies, we cannot understand the differences
believed to exist in this respect between the various races of mankind.
Even the partial transmission of virtuous tendencies would be an immense
assistance to the primary impulse derived directly and indirectly from the
social instincts. Admitting for a moment that virtuous tendencies are
inherited, it appears probable, at least in such cases as chastity,
temperance, humanity to animals, etc., that they become first impressed on
the mental organization through habit, instruction and example, continued
during several generations in the same family, and in a quite subordinate
degree, or not at all, by the individuals possessing such virtues having
succeeded best in the struggle for life. My chief source of doubt with
respect to any such inheritance, is that senseless customs, superstitions,
and tastes, such as the horror of a Hindoo for unclean food, ought on the
same principle to be transmitted. I have not met with any evidence in
support of the transmission of superstitious customs or senseless habits,
although in itself it is perhaps not less probable than that animals should
acquire inherited tastes for certain kinds of food or fear of certain foes.
Finally the social instincts, which no doubt were acquired by man as by the
lower animals for the good of the community, will from the first have given
to him some wish to aid his fellows, some feeling of sympathy, and have
compelled him to regard their approbation and disapprobation. Such
impulses will have served him at a very early period as a rude rule of
right and wrong. But as man gradually advanced in intellectual power, and
was enabled to trace the more remote consequences of his actions; as he
acquired sufficient knowledge to reject baneful customs and superstitions;
as he regarded more and more, not only the welfare, but the happiness of
his fellow-men; as from habit, following on beneficial experience,
instruction and example, his sympathies became more tender and widely
diffused, extending to men of all races, to the imbecile, maimed, and other
useless members of society, and finally to the lower animals,--so would the
standard of his morality rise higher and higher. And it is admitted by
moralists of the derivative school and by some intuitionists, that the
standard of morality has risen since an early period in the history of man.
(48. A writer in the 'North British Review' (July 1869, p. 531), well
capable of forming a sound judgment, expresses himself strongly in favour
of this conclusion. Mr. Lecky ('History of Morals,' vol. i. p. 143) seems
to a certain extent to coincide therein.)
As a struggle may sometimes be seen going on between the various instincts
of the lower animals, it is not surprising that there should be a struggle
in man between his social instincts, with their derived virtues, and his
lower, though momentarily stronger impulses or desires. This, as Mr.
Galton (49. See his remarkable work on 'Hereditary Genius,' 1869, p. 349.
The Duke of Argyll ('Primeval Man,' 1869, p. 188) has some good remarks on
the contest in man's nature between right and wrong.) has remarked, is all
the less surprising, as man has emerged from a state of barbarism within a
comparatively recent period. After having yielded to some temptation we
feel a sense of dissatisfaction, shame, repentance, or remorse, analogous
to the feelings caused by other powerful instincts or desires, when left
unsatisfied or baulked. We compare the weakened impression of a past
temptation with the ever present social instincts, or with habits, gained
in early youth and strengthened during our whole lives, until they have
become almost as strong as instincts. If with the temptation still before
us we do not yield, it is because either the social instinct or some custom
is at the moment predominant, or because we have learnt that it will appear
to us hereafter the stronger, when compared with the weakened impression of
the temptation, and we realise that its violation would cause us suffering.
Looking to future generations, there is no cause to fear that the social
instincts will grow weaker, and we may expect that virtuous habits will
grow stronger, becoming perhaps fixed by inheritance. In this case the
struggle between our higher and lower impulses will be less severe, and
virtue will be triumphant.
SUMMARY OF THE LAST TWO CHAPTERS.
There can be no doubt that the difference between the mind of the lowest
man and that of the highest animal is immense. An anthropomorphous ape, if
he could take a dispassionate view of his own case, would admit that though
he could form an artful plan to plunder a garden--though he could use
stones for fighting or for breaking open nuts, yet that the thought of
fashioning a stone into a tool was quite beyond his scope. Still less, as
he would admit, could he follow out a train of metaphysical reasoning, or
solve a mathematical problem, or reflect on God, or admire a grand natural
scene. Some apes, however, would probably declare that they could and did
admire the beauty of the coloured skin and fur of their partners in
marriage. They would admit, that though they could make other apes
understand by cries some of their perceptions and simpler wants, the notion
of expressing definite ideas by definite sounds had never crossed their
minds. They might insist that they were ready to aid their fellow-apes of
the same troop in many ways, to risk their lives for them, and to take
charge of their orphans; but they would be forced to acknowledge that
disinterested love for all living creatures, the most noble attribute of
man, was quite beyond their comprehension.
Nevertheless the difference in mind between man and the higher animals,
great as it is, certainly is one of degree and not of kind. We have seen
that the senses and intuitions, the various emotions and faculties, such as
love, memory, attention, curiosity, imitation, reason, etc., of which man
boasts, may be found in an incipient, or even sometimes in a well-developed
condition, in the lower animals. They are also capable of some inherited
improvement, as we see in the domestic dog compared with the wolf or
jackal. If it could be proved that certain high mental powers, such as the
formation of general concepts, self-consciousness, etc., were absolutely
peculiar to man, which seems extremely doubtful, it is not improbable that
these qualities are merely the incidental results of other highly-advanced
intellectual faculties; and these again mainly the result of the continued
use of a perfect language. At what age does the new-born infant possess
the power of abstraction, or become self-conscious, and reflect on its own
existence? We cannot answer; nor can we answer in regard to the ascending
organic scale. The half-art, half-instinct of language still bears the
stamp of its gradual evolution. The ennobling belief in God is not
universal with man; and the belief in spiritual agencies naturally follows
from other mental powers. The moral sense perhaps affords the best and
highest distinction between man and the lower animals; but I need say
nothing on this head, as I have so lately endeavoured to shew that the
social instincts,--the prime principle of man's moral constitution (50.
'The Thoughts of Marcus Aurelius,' etc., p. 139.)--with the aid of active
intellectual powers and the effects of habit, naturally lead to the golden
rule, "As ye would that men should do to you, do ye to them likewise;" and
this lies at the foundation of morality.
In the next chapter I shall make some few remarks on the probable steps and
means by which the several mental and moral faculties of man have been
gradually evolved. That such evolution is at least possible, ought not to
be denied, for we daily see these faculties developing in every infant; and
we may trace a perfect gradation from the mind of an utter idiot, lower
than that of an animal low in the scale, to the mind of a Newton.
CHAPTER V.
ON THE DEVELOPMENT OF THE INTELLECTUAL AND MORAL FACULTIES DURING PRIMEVAL
AND CIVILISED TIMES.
Advancement of the intellectual powers through natural selection--
Importance of imitation--Social and moral faculties--Their development
within the limits of the same tribe--Natural selection as affecting
civilised nations--Evidence that civilised nations were once barbarous.
The subjects to be discussed in this chapter are of the highest interest,
but are treated by me in an imperfect and fragmentary manner. Mr. Wallace,
in an admirable paper before referred to (1. Anthropological Review, May
1864, p. clviii.), argues that man, after he had partially acquired those
intellectual and moral faculties which distinguish him from the lower
animals, would have been but little liable to bodily modifications through
natural selection or any other means. For man is enabled through his
mental faculties "to keep with an unchanged body in harmony with the
changing universe." He has great power of adapting his habits to new
conditions of life. He invents weapons, tools, and various stratagems to
procure food and to defend himself. When he migrates into a colder climate
he uses clothes, builds sheds, and makes fires; and by the aid of fire
cooks food otherwise indigestible. He aids his fellow-men in many ways,
and anticipates future events. Even at a remote period he practised some
division of labour.
The lower animals, on the other hand, must have their bodily structure
modified in order to survive under greatly changed conditions. They must
be rendered stronger, or acquire more effective teeth or claws, for defence
against new enemies; or they must be reduced in size, so as to escape
detection and danger. When they migrate into a colder climate, they must
become clothed with thicker fur, or have their constitutions altered. If
they fail to be thus modified, they will cease to exist.
The case, however, is widely different, as Mr. Wallace has with justice
insisted, in relation to the intellectual and moral faculties of man.
These faculties are variable; and we have every reason to believe that the
variations tend to be inherited. Therefore, if they were formerly of high
importance to primeval man and to his ape-like progenitors, they would have
been perfected or advanced through natural selection. Of the high
importance of the intellectual faculties there can be no doubt, for man
mainly owes to them his predominant position in the world. We can see,
that in the rudest state of society, the individuals who were the most
sagacious, who invented and used the best weapons or traps, and who were
best able to defend themselves, would rear the greatest number of
offspring. The tribes, which included the largest number of men thus
endowed, would increase in number and supplant other tribes. Numbers
depend primarily on the means of subsistence, and this depends partly on
the physical nature of the country, but in a much higher degree on the arts
which are there practised. As a tribe increases and is victorious, it is
often still further increased by the absorption of other tribes. (2.
After a time the members or tribes which are absorbed into another tribe
assume, as Sir Henry Maine remarks ('Ancient Law,' 1861, p. 131), that they
are the co-descendants of the same ancestors.) The stature and strength of
the men of a tribe are likewise of some importance for its success, and
these depend in part on the nature and amount of the food which can be
obtained. In Europe the men of the Bronze period were supplanted by a race
more powerful, and, judging from their sword-handles, with larger hands (3.
Morlot, 'Soc. Vaud. Sc. Nat.' 1860, p. 294.); but their success was
probably still more due to their superiority in the arts.
All that we know about savages, or may infer from their traditions and from
old monuments, the history of which is quite forgotten by the present
inhabitants, shew that from the remotest times successful tribes have
supplanted other tribes. Relics of extinct or forgotten tribes have been
discovered throughout the civilised regions of the earth, on the wild
plains of America, and on the isolated islands in the Pacific Ocean. At
the present day civilised nations are everywhere supplanting barbarous
nations, excepting where the climate opposes a deadly barrier; and they
succeed mainly, though not exclusively, through their arts, which are the
products of the intellect. It is, therefore, highly probable that with
mankind the intellectual faculties have been mainly and gradually perfected
through natural selection; and this conclusion is sufficient for our
purpose. Undoubtedly it would be interesting to trace the development of
each separate faculty from the state in which it exists in the lower
animals to that in which it exists in man; but neither my ability nor
knowledge permits the attempt.
It deserves notice that, as soon as the progenitors of man became social
(and this probably occurred at a very early period), the principle of
imitation, and reason, and experience would have increased, and much
modified the intellectual powers in a way, of which we see only traces in
the lower animals. Apes are much given to imitation, as are the lowest
savages; and the simple fact previously referred to, that after a time no
animal can be caught in the same place by the same sort of trap, shews that
animals learn by experience, and imitate the caution of others. Now, if
some one man in a tribe, more sagacious than the others, invented a new
snare or weapon, or other means of attack or defence, the plainest self-
interest, without the assistance of much reasoning power, would prompt the
other members to imitate him; and all would thus profit. The habitual
practice of each new art must likewise in some slight degree strengthen the
intellect. If the new invention were an important one, the tribe would
increase in number, spread, and supplant other tribes. In a tribe thus
rendered more numerous there would always be a rather greater chance of the
birth of other superior and inventive members. If such men left children
to inherit their mental superiority, the chance of the birth of still more
ingenious members would be somewhat better, and in a very small tribe
decidedly better. Even if they left no children, the tribe would still
include their blood-relations; and it has been ascertained by
agriculturists (4. I have given instances in my Variation of Animals under
Domestication, vol. ii. p. 196.) that by preserving and breeding from the
family of an animal, which when slaughtered was found to be valuable, the
desired character has been obtained.
Turning now to the social and moral faculties. In order that primeval men,
or the ape-like progenitors of man, should become social, they must have
acquired the same instinctive feelings, which impel other animals to live
in a body; and they no doubt exhibited the same general disposition. They
would have felt uneasy when separated from their comrades, for whom they
would have felt some degree of love; they would have warned each other of
danger, and have given mutual aid in attack or defence. All this implies
some degree of sympathy, fidelity, and courage. Such social qualities, the
paramount importance of which to the lower animals is disputed by no one,
were no doubt acquired by the progenitors of man in a similar manner,
namely, through natural selection, aided by inherited habit. When two
tribes of primeval man, living in the same country, came into competition,
if (other circumstances being equal) the one tribe included a great number
of courageous, sympathetic and faithful members, who were always ready to
warn each other of danger, to aid and defend each other, this tribe would
succeed better and conquer the other. Let it be borne in mind how all-
important in the never-ceasing wars of savages, fidelity and courage must
be. The advantage which disciplined soldiers have over undisciplined
hordes follows chiefly from the confidence which each man feels in his
comrades. Obedience, as Mr. Bagehot has well shewn (5. See a remarkable
series of articles on 'Physics and Politics,' in the 'Fortnightly Review,'
Nov. 1867; April 1, 1868; July 1, 1869, since separately published.), is of
the highest value, for any form of government is better than none. Selfish
and contentious people will not cohere, and without coherence nothing can
be effected. A tribe rich in the above qualities would spread and be
victorious over other tribes: but in the course of time it would, judging
from all past history, be in its turn overcome by some other tribe still
more highly endowed. Thus the social and moral qualities would tend slowly
to advance and be diffused throughout the world.
But it may be asked, how within the limits of the same tribe did a large
number of members first become endowed with these social and moral
qualities, and how was the standard of excellence raised? It is extremely
doubtful whether the offspring of the more sympathetic and benevolent
parents, or of those who were the most faithful to their comrades, would be
reared in greater numbers than the children of selfish and treacherous
parents belonging to the same tribe. He who was ready to sacrifice his
life, as many a savage has been, rather than betray his comrades, would
often leave no offspring to inherit his noble nature. The bravest men, who
were always willing to come to the front in war, and who freely risked
their lives for others, would on an average perish in larger numbers than
other men. Therefore, it hardly seems probable, that the number of men
gifted with such virtues, or that the standard of their excellence, could
be increased through natural selection, that is, by the survival of the
fittest; for we are not here speaking of one tribe being victorious over
another.
Although the circumstances, leading to an increase in the number of those
thus endowed within the same tribe, are too complex to be clearly followed
out, we can trace some of the probable steps. In the first place, as the
reasoning powers and foresight of the members became improved, each man
would soon learn that if he aided his fellow-men, he would commonly receive
aid in return. From this low motive he might acquire the habit of aiding
his fellows; and the habit of performing benevolent actions certainly
strengthens the feeling of sympathy which gives the first impulse to
benevolent actions. Habits, moreover, followed during many generations
probably tend to be inherited.
But another and much more powerful stimulus to the development of the
social virtues, is afforded by the praise and the blame of our fellow-men.
To the instinct of sympathy, as we have already seen, it is primarily due,
that we habitually bestow both praise and blame on others, whilst we love
the former and dread the latter when applied to ourselves; and this
instinct no doubt was originally acquired, like all the other social
instincts, through natural selection. At how early a period the
progenitors of man in the course of their development, became capable of
feeling and being impelled by, the praise or blame of their fellow-
creatures, we cannot of course say. But it appears that even dogs
appreciate encouragement, praise, and blame. The rudest savages feel the
sentiment of glory, as they clearly shew by preserving the trophies of
their prowess, by their habit of excessive boasting, and even by the
extreme care which they take of their personal appearance and decorations;
for unless they regarded the opinion of their comrades, such habits would
be senseless.
They certainly feel shame at the breach of some of their lesser rules, and
apparently remorse, as shewn by the case of the Australian who grew thin
and could not rest from having delayed to murder some other woman, so as to
propitiate his dead wife's spirit. Though I have not met with any other
recorded case, it is scarcely credible that a savage, who will sacrifice
his life rather than betray his tribe, or one who will deliver himself up
as a prisoner rather than break his parole (6. Mr. Wallace gives cases in
his 'Contributions to the Theory of Natural Selection,' 1870, p. 354.),
would not feel remorse in his inmost soul, if he had failed in a duty,
which he held sacred.
We may therefore conclude that primeval man, at a very remote period, was
influenced by the praise and blame of his fellows. It is obvious, that the
members of the same tribe would approve of conduct which appeared to them
to be for the general good, and would reprobate that which appeared evil.
To do good unto others--to do unto others as ye would they should do unto
you--is the foundation-stone of morality. It is, therefore, hardly
possible to exaggerate the importance during rude times of the love of
praise and the dread of blame. A man who was not impelled by any deep,
instinctive feeling, to sacrifice his life for the good of others, yet was
roused to such actions by a sense of glory, would by his example excite the
same wish for glory in other men, and would strengthen by exercise the
noble feeling of admiration. He might thus do far more good to his tribe
than by begetting offspring with a tendency to inherit his own high
character.
With increased experience and reason, man perceives the more remote
consequences of his actions, and the self-regarding virtues, such as
temperance, chastity, etc., which during early times are, as we have before
seen, utterly disregarded, come to be highly esteemed or even held sacred.
I need not, however, repeat what I have said on this head in the fourth
chapter. Ultimately our moral sense or conscience becomes a highly complex
sentiment--originating in the social instincts, largely guided by the
approbation of our fellow-men, ruled by reason, self-interest, and in later
times by deep religious feelings, and confirmed by instruction and habit.
It must not be forgotten that although a high standard of morality gives
but a slight or no advantage to each individual man and his children over
the other men of the same tribe, yet that an increase in the number of
well-endowed men and an advancement in the standard of morality will
certainly give an immense advantage to one tribe over another. A tribe
including many members who, from possessing in a high degree the spirit of
patriotism, fidelity, obedience, courage, and sympathy, were always ready
to aid one another, and to sacrifice themselves for the common good, would
be victorious over most other tribes; and this would be natural selection.
At all times throughout the world tribes have supplanted other tribes; and
as morality is one important element in their success, the standard of
morality and the number of well-endowed men will thus everywhere tend to
rise and increase.
It is, however, very difficult to form any judgment why one particular
tribe and not another has been successful and has risen in the scale of
civilisation. Many savages are in the same condition as when first
discovered several centuries ago. As Mr. Bagehot has remarked, we are apt
to look at progress as normal in human society; but history refutes this.
The ancients did not even entertain the idea, nor do the Oriental nations
at the present day. According to another high authority, Sir Henry Maine
(7. 'Ancient Law,' 1861, p. 22. For Mr. Bagehot's remarks, 'Fortnightly
Review,' April 1, 1868, p. 452.), "the greatest part of mankind has never
shewn a particle of desire that its civil institutions should be improved."
Progress seems to depend on many concurrent favourable conditions, far too
complex to be followed out. But it has often been remarked, that a cool
climate, from leading to industry and to the various arts, has been highly
favourable thereto. The Esquimaux, pressed by hard necessity, have
succeeded in many ingenious inventions, but their climate has been too
severe for continued progress. Nomadic habits, whether over wide plains,
or through the dense forests of the tropics, or along the shores of the
sea, have in every case been highly detrimental. Whilst observing the
barbarous inhabitants of Tierra del Fuego, it struck me that the possession
of some property, a fixed abode, and the union of many families under a
chief, were the indispensable requisites for civilisation. Such habits
almost necessitate the cultivation of the ground; and the first steps in
cultivation would probably result, as I have elsewhere shewn (8. 'The
Variation of Animals and Plants under Domestication,' vol. i. p. 309.),
from some such accident as the seeds of a fruit-tree falling on a heap of
refuse, and producing an unusually fine variety. The problem, however, of
the first advance of savages towards civilisation is at present much too
difficult to be solved.
NATURAL SELECTION AS AFFECTING CIVILISED NATIONS.
I have hitherto only considered the advancement of man from a semi-human
condition to that of the modern savage. But some remarks on the action of
natural selection on civilised nations may be worth adding. This subject
has been ably discussed by Mr. W.R. Greg (9. 'Fraser's Magazine,' Sept.
1868, p. 353. This article seems to have struck many persons, and has
given rise to two remarkable essays and a rejoinder in the 'Spectator,'
Oct. 3rd and 17th, 1868. It has also been discussed in the 'Quarterly
Journal of Science,' 1869, p. 152, and by Mr. Lawson Tait in the 'Dublin
Quarterly Journal of Medical Science,' Feb. 1869, and by Mr. E. Ray
Lankester in his 'Comparative Longevity,' 1870, p. 128. Similar views
appeared previously in the 'Australasian,' July 13, 1867. I have borrowed
ideas from several of these writers.), and previously by Mr. Wallace and
Mr. Galton. (10. For Mr. Wallace, see 'Anthropological Review,' as before
cited. Mr. Galton in 'Macmillan's Magazine,' Aug. 1865, p. 318; also his
great work, 'Hereditary Genius,' 1870.) Most of my remarks are taken from
these three authors. With savages, the weak in body or mind are soon
eliminated; and those that survive commonly exhibit a vigorous state of
health. We civilised men, on the other hand, do our utmost to check the
process of elimination; we build asylums for the imbecile, the maimed, and
the sick; we institute poor-laws; and our medical men exert their utmost
skill to save the life of every one to the last moment. There is reason to
believe that vaccination has preserved thousands, who from a weak
constitution would formerly have succumbed to small-pox. Thus the weak
members of civilised societies propagate their kind. No one who has
attended to the breeding of domestic animals will doubt that this must be
highly injurious to the race of man. It is surprising how soon a want of
care, or care wrongly directed, leads to the degeneration of a domestic
race; but excepting in the case of man himself, hardly any one is so
ignorant as to allow his worst animals to breed.
The aid which we feel impelled to give to the helpless is mainly an
incidental result of the instinct of sympathy, which was originally
acquired as part of the social instincts, but subsequently rendered, in the
manner previously indicated, more tender and more widely diffused. Nor
could we check our sympathy, even at the urging of hard reason, without
deterioration in the noblest part of our nature. The surgeon may harden
himself whilst performing an operation, for he knows that he is acting for
the good of his patient; but if we were intentionally to neglect the weak
and helpless, it could only be for a contingent benefit, with an
overwhelming present evil. We must therefore bear the undoubtedly bad
effects of the weak surviving and propagating their kind; but there appears
to be at least one check in steady action, namely that the weaker and
inferior members of society do not marry so freely as the sound; and this
check might be indefinitely increased by the weak in body or mind
refraining from marriage, though this is more to be hoped for than
expected.
In every country in which a large standing army is kept up, the finest
young men are taken by the conscription or are enlisted. They are thus
exposed to early death during war, are often tempted into vice, and are
prevented from marrying during the prime of life. On the other hand the
shorter and feebler men, with poor constitutions, are left at home, and
consequently have a much better chance of marrying and propagating their
kind. (11. Prof. H. Fick ('Einfluss der Naturwissenschaft auf das Recht,'
June 1872) has some good remarks on this head, and on other such points.)
Man accumulates property and bequeaths it to his children, so that the
children of the rich have an advantage over the poor in the race for
success, independently of bodily or mental superiority. On the other hand,
the children of parents who are short-lived, and are therefore on an
average deficient in health and vigour, come into their property sooner
than other children, and will be likely to marry earlier, and leave a
larger number of offspring to inherit their inferior constitutions. But
the inheritance of property by itself is very far from an evil; for without
the accumulation of capital the arts could not progress; and it is chiefly
through their power that the civilised races have extended, and are now
everywhere extending their range, so as to take the place of the lower
races. Nor does the moderate accumulation of wealth interfere with the
process of selection. When a poor man becomes moderately rich, his
children enter trades or professions in which there is struggle enough, so
that the able in body and mind succeed best. The presence of a body of
well-instructed men, who have not to labour for their daily bread, is
important to a degree which cannot be over-estimated; as all high
intellectual work is carried on by them, and on such work, material
progress of all kinds mainly depends, not to mention other and higher
advantages. No doubt wealth when very great tends to convert men into
useless drones, but their number is never large; and some degree of
elimination here occurs, for we daily see rich men, who happen to be fools
or profligate, squandering away their wealth.
Primogeniture with entailed estates is a more direct evil, though it may
formerly have been a great advantage by the creation of a dominant class,
and any government is better than none. Most eldest sons, though they may
be weak in body or mind, marry, whilst the younger sons, however superior
in these respects, do not so generally marry. Nor can worthless eldest
sons with entailed estates squander their wealth. But here, as elsewhere,
the relations of civilised life are so complex that some compensatory
checks intervene. The men who are rich through primogeniture are able to
select generation after generation the more beautiful and charming women;
and these must generally be healthy in body and active in mind. The evil
consequences, such as they may be, of the continued preservation of the
same line of descent, without any selection, are checked by men of rank
always wishing to increase their wealth and power; and this they effect by
marrying heiresses. But the daughters of parents who have produced single
children, are themselves, as Mr. Galton (12. 'Hereditary Genius,' 1870, pp.
132-140.) has shewn, apt to be sterile; and thus noble families are
continually cut off in the direct line, and their wealth flows into some
side channel; but unfortunately this channel is not determined by
superiority of any kind.
Although civilisation thus checks in many ways the action of natural
selection, it apparently favours the better development of the body, by
means of good food and the freedom from occasional hardships. This may be
inferred from civilised men having been found, wherever compared, to be
physically stronger than savages. (13. Quatrefages, 'Revue des Cours
Scientifiques,' 1867-68, p. 659.) They appear also to have equal powers of
endurance, as has been proved in many adventurous expeditions. Even the
great luxury of the rich can be but little detrimental; for the expectation
of life of our aristocracy, at all ages and of both sexes, is very little
inferior to that of healthy English lives in the lower classes. (14.
See the fifth and sixth columns, compiled from good authorities, in the
table given in Mr. E.R. Lankester's 'Comparative Longevity,' 1870, p. 115.)
We will now look to the intellectual faculties. If in each grade of
society the members were divided into two equal bodies, the one including
the intellectually superior and the other the inferior, there can be little
doubt that the former would succeed best in all occupations, and rear a
greater number of children. Even in the lowest walks of life, skill and
ability must be of some advantage; though in many occupations, owing to the
great division of labour, a very small one. Hence in civilised nations
there will be some tendency to an increase both in the number and in the
standard of the intellectually able. But I do not wish to assert that this
tendency may not be more than counterbalanced in other ways, as by the
multiplication of the reckless and improvident; but even to such as these,
ability must be some advantage.
It has often been objected to views like the foregoing, that the most
eminent men who have ever lived have left no offspring to inherit their
great intellect. Mr. Galton says, "I regret I am unable to solve the
simple question whether, and how far, men and women who are prodigies of
genius are infertile. I have, however, shewn that men of eminence are by
no means so." (15. 'Hereditary Genius,' 1870, p. 330.) Great lawgivers,
the founders of beneficent religions, great philosophers and discoverers in
science, aid the progress of mankind in a far higher degree by their works
than by leaving a numerous progeny. In the case of corporeal structures,
it is the selection of the slightly better-endowed and the elimination of
the slightly less well-endowed individuals, and not the preservation of
strongly-marked and rare anomalies, that leads to the advancement of a
species. (16. 'Origin of Species' (fifth edition, 1869), p. 104.) So it
will be with the intellectual faculties, since the somewhat abler men in
each grade of society succeed rather better than the less able, and
consequently increase in number, if not otherwise prevented. When in any
nation the standard of intellect and the number of intellectual men have
increased, we may expect from the law of the deviation from an average,
that prodigies of genius will, as shewn by Mr. Galton, appear somewhat more
frequently than before.
In regard to the moral qualities, some elimination of the worst
dispositions is always in progress even in the most civilised nations.
Malefactors are executed, or imprisoned for long periods, so that they
cannot freely transmit their bad qualities. Melancholic and insane persons
are confined, or commit suicide. Violent and quarrelsome men often come to
a bloody end. The restless who will not follow any steady occupation--and
this relic of barbarism is a great check to civilisation (17. 'Hereditary
Genius,' 1870, p. 347.)--emigrate to newly-settled countries; where they
prove useful pioneers. Intemperance is so highly destructive, that the
expectation of life of the intemperate, at the age of thirty for instance,
is only 13.8 years; whilst for the rural labourers of England at the same
age it is 40.59 years. (18. E. Ray Lankester, 'Comparative Longevity,'
1870, p. 115. The table of the intemperate is from Neison's 'Vital
Statistics.' In regard to profligacy, see Dr. Farr, 'Influence of Marriage
on Mortality,' 'Nat. Assoc. for the Promotion of Social Science,' 1858.)
Profligate women bear few children, and profligate men rarely marry; both
suffer from disease. In the breeding of domestic animals, the elimination
of those individuals, though few in number, which are in any marked manner
inferior, is by no means an unimportant element towards success. This
especially holds good with injurious characters which tend to reappear
through reversion, such as blackness in sheep; and with mankind some of the
worst dispositions, which occasionally without any assignable cause make
their appearance in families, may perhaps be reversions to a savage state,
from which we are not removed by very many generations. This view seems
indeed recognised in the common expression that such men are the black
sheep of the family.
With civilised nations, as far as an advanced standard of morality, and an
increased number of fairly good men are concerned, natural selection
apparently effects but little; though the fundamental social instincts were
originally thus gained. But I have already said enough, whilst treating of
the lower races, on the causes which lead to the advance of morality,
namely, the approbation of our fellow-men--the strengthening of our
sympathies by habit--example and imitation--reason--experience, and even
self-interest--instruction during youth, and religious feelings.
A most important obstacle in civilised countries to an increase in the
number of men of a superior class has been strongly insisted on by Mr. Greg
and Mr. Galton (19. 'Fraser's Magazine,' Sept. 1868, p. 353. 'Macmillan's
Magazine,' Aug. 1865, p. 318. The Rev. F.W. Farrar ('Fraser's Magazine,'
Aug. 1870, p. 264) takes a different view.), namely, the fact that the very
poor and reckless, who are often degraded by vice, almost invariably marry
early, whilst the careful and frugal, who are generally otherwise virtuous,
marry late in life, so that they may be able to support themselves and
their children in comfort. Those who marry early produce within a given
period not only a greater number of generations, but, as shewn by Dr.
Duncan (20. 'On the Laws of the Fertility of Women,' in 'Transactions of
the Royal Society,' Edinburgh, vol. xxiv. p. 287; now published separately
under the title of 'Fecundity, Fertility, and Sterility,' 1871. See, also,
Mr. Galton, 'Hereditary Genius,' pp. 352-357, for observations to the above
effect.), they produce many more children. The children, moreover, that
are borne by mothers during the prime of life are heavier and larger, and
therefore probably more vigorous, than those born at other periods. Thus
the reckless, degraded, and often vicious members of society, tend to
increase at a quicker rate than the provident and generally virtuous
members. Or as Mr. Greg puts the case: "The careless, squalid, unaspiring
Irishman multiplies like rabbits: the frugal, foreseeing, self-respecting,
ambitious Scot, stern in his morality, spiritual in his faith, sagacious
and disciplined in his intelligence, passes his best years in struggle and
in celibacy, marries late, and leaves few behind him. Given a land
originally peopled by a thousand Saxons and a thousand Celts--and in a
dozen generations five-sixths of the population would be Celts, but five-
sixths of the property, of the power, of the intellect, would belong to the
one-sixth of Saxons that remained. In the eternal 'struggle for
existence,' it would be the inferior and LESS favoured race that had
prevailed--and prevailed by virtue not of its good qualities but of its
faults."
There are, however, some checks to this downward tendency. We have seen
that the intemperate suffer from a high rate of mortality, and the
extremely profligate leave few offspring. The poorest classes crowd into
towns, and it has been proved by Dr. Stark from the statistics of ten years
in Scotland (21. 'Tenth Annual Report of Births, Deaths, etc., in
Scotland,' 1867, p. xxix.), that at all ages the death-rate is higher in
towns than in rural districts, "and during the first five years of life the
town death-rate is almost exactly double that of the rural districts." As
these returns include both the rich and the poor, no doubt more than twice
the number of births would be requisite to keep up the number of the very
poor inhabitants in the towns, relatively to those in the country. With
women, marriage at too early an age is highly injurious; for it has been
found in France that, "Twice as many wives under twenty die in the year, as
died out of the same number of the unmarried." The mortality, also, of
husbands under twenty is "excessively high" (22. These quotations are
taken from our highest authority on such questions, namely, Dr. Farr, in
his paper 'On the Influence of Marriage on the Mortality of the French
People,' read before the Nat. Assoc. for the Promotion of Social Science,
1858.), but what the cause of this may be, seems doubtful. Lastly, if the
men who prudently delay marrying until they can bring up their families in
comfort, were to select, as they often do, women in the prime of life, the
rate of increase in the better class would be only slightly lessened.
It was established from an enormous body of statistics, taken during 1853,
that the unmarried men throughout France, between the ages of twenty and
eighty, die in a much larger proportion than the married: for instance,
out of every 1000 unmarried men, between the ages of twenty and thirty,
11.3 annually died, whilst of the married, only 6.5 died. (23. Dr. Farr,
ibid. The quotations given below are extracted from the same striking
paper.) A similar law was proved to hold good, during the years 1863 and
1864, with the entire population above the age of twenty in Scotland: for
instance, out of every 1000 unmarried men, between the ages of twenty and
thirty, 14.97 annually died, whilst of the married only 7.24 died, that is
less than half. (24. I have taken the mean of the quinquennial means,
given in 'The Tenth Annual Report of Births, Deaths, etc., in Scotland,'
1867. The quotation from Dr. Stark is copied from an article in the 'Daily
News,' Oct. 17, 1868, which Dr. Farr considers very carefully written.)
Dr. Stark remarks on this, "Bachelorhood is more destructive to life than
the most unwholesome trades, or than residence in an unwholesome house or
district where there has never been the most distant attempt at sanitary
improvement." He considers that the lessened mortality is the direct
result of "marriage, and the more regular domestic habits which attend that
state." He admits, however, that the intemperate, profligate, and criminal
classes, whose duration of life is low, do not commonly marry; and it must
likewise be admitted that men with a weak constitution, ill health, or any
great infirmity in body or mind, will often not wish to marry, or will be
rejected. Dr. Stark seems to have come to the conclusion that marriage in
itself is a main cause of prolonged life, from finding that aged married
men still have a considerable advantage in this respect over the unmarried
of the same advanced age; but every one must have known instances of men,
who with weak health during youth did not marry, and yet have survived to
old age, though remaining weak, and therefore always with a lessened chance
of life or of marrying. There is another remarkable circumstance which
seems to support Dr. Stark's conclusion, namely, that widows and widowers
in France suffer in comparison with the married a very heavy rate of
mortality; but Dr. Farr attributes this to the poverty and evil habits
consequent on the disruption of the family, and to grief. On the whole we
may conclude with Dr. Farr that the lesser mortality of married than of
unmarried men, which seems to be a general law, "is mainly due to the
constant elimination of imperfect types, and to the skilful selection of
the finest individuals out of each successive generation;" the selection
relating only to the marriage state, and acting on all corporeal,
intellectual, and moral qualities. (25. Dr. Duncan remarks ('Fecundity,
Fertility, etc.' 1871, p. 334) on this subject: "At every age the healthy
and beautiful go over from the unmarried side to the married, leaving the
unmarried columns crowded with the sickly and unfortunate.") We may,
therefore, infer that sound and good men who out of prudence remain for a
time unmarried, do not suffer a high rate of mortality.
If the various checks specified in the two last paragraphs, and perhaps
others as yet unknown, do not prevent the reckless, the vicious and
otherwise inferior members of society from increasing at a quicker rate
than the better class of men, the nation will retrograde, as has too often
occurred in the history of the world. We must remember that progress is no
invariable rule. It is very difficult to say why one civilised nation
rises, becomes more powerful, and spreads more widely, than another; or why
the same nation progresses more quickly at one time than at another. We
can only say that it depends on an increase in the actual number of the
population, on the number of men endowed with high intellectual and moral
faculties, as well as on their standard of excellence. Corporeal structure
appears to have little influence, except so far as vigour of body leads to
vigour of mind.
It has been urged by several writers that as high intellectual powers are
advantageous to a nation, the old Greeks, who stood some grades higher in
intellect than any race that has ever existed (26. See the ingenious and
original argument on this subject by Mr. Galton, 'Hereditary Genius,' pp.
340-342.), ought, if the power of natural selection were real, to have
risen still higher in the scale, increased in number, and stocked the whole
of Europe. Here we have the tacit assumption, so often made with respect
to corporeal structures, that there is some innate tendency towards
continued development in mind and body. But development of all kinds
depends on many concurrent favourable circumstances. Natural selection
acts only tentatively. Individuals and races may have acquired certain
indisputable advantages, and yet have perished from failing in other
characters. The Greeks may have retrograded from a want of coherence
between the many small states, from the small size of their whole country,
from the practice of slavery, or from extreme sensuality; for they did not
succumb until "they were enervated and corrupt to the very core." (27.
Mr. Greg, 'Fraser's Magazine,' Sept. 1868, p. 357.) The western nations of
Europe, who now so immeasurably surpass their former savage progenitors,
and stand at the summit of civilisation, owe little or none of their
superiority to direct inheritance from the old Greeks, though they owe much
to the written works of that wonderful people.
Who can positively say why the Spanish nation, so dominant at one time, has
been distanced in the race. The awakening of the nations of Europe from
the dark ages is a still more perplexing problem. At that early period, as
Mr. Galton has remarked, almost all the men of a gentle nature, those given
to meditation or culture of the mind, had no refuge except in the bosom of
a Church which demanded celibacy (28. 'Hereditary Genius,' 1870, pp. 357-
359. The Rev. F.W. Farrar ('Fraser's Magazine,' Aug. 1870, p. 257)
advances arguments on the other side. Sir C. Lyell had already
('Principles of Geology,' vol. ii. 1868, p. 489), in a striking passage
called attention to the evil influence of the Holy Inquisition in having,
through selection, lowered the general standard of intelligence in
Europe.); and this could hardly fail to have had a deteriorating influence
on each successive generation. During this same period the Holy
Inquisition selected with extreme care the freest and boldest men in order
to burn or imprison them. In Spain alone some of the best men--those who
doubted and questioned, and without doubting there can be no progress--were
eliminated during three centuries at the rate of a thousand a year. The
evil which the Catholic Church has thus effected is incalculable, though no
doubt counterbalanced to a certain, perhaps to a large, extent in other
ways; nevertheless, Europe has progressed at an unparalleled rate.
The remarkable success of the English as colonists, compared to other
European nations, has been ascribed to their "daring and persistent
energy"; a result which is well illustrated by comparing the progress of
the Canadians of English and French extraction; but who can say how the
English gained their energy? There is apparently much truth in the belief
that the wonderful progress of the United States, as well as the character
of the people, are the results of natural selection; for the more
energetic, restless, and courageous men from all parts of Europe have
emigrated during the last ten or twelve generations to that great country,
and have there succeeded best. (29. Mr. Galton, 'Macmillan's Magazine,'
August 1865, p. 325. See also, 'Nature,' 'On Darwinism and National Life,'
Dec. 1869, p. 184.) Looking to the distant future, I do not think that the
Rev. Mr. Zincke takes an exaggerated view when he says (30. 'Last Winter
in the United States,' 1868, p. 29.): "All other series of events--as that
which resulted in the culture of mind in Greece, and that which resulted in
the empire of Rome--only appear to have purpose and value when viewed in
connection with, or rather as subsidiary to...the great stream of Anglo-
Saxon emigration to the west." Obscure as is the problem of the advance of
civilisation, we can at least see that a nation which produced during a
lengthened period the greatest number of highly intellectual, energetic,
brave, patriotic, and benevolent men, would generally prevail over less
favoured nations.
Natural selection follows from the struggle for existence; and this from a
rapid rate of increase. It is impossible not to regret bitterly, but
whether wisely is another question, the rate at which man tends to
increase; for this leads in barbarous tribes to infanticide and many other
evils, and in civilised nations to abject poverty, celibacy, and to the
late marriages of the prudent. But as man suffers from the same physical
evils as the lower animals, he has no right to expect an immunity from the
evils consequent on the struggle for existence. Had he not been subjected
during primeval times to natural selection, assuredly he would never have
attained to his present rank. Since we see in many parts of the world
enormous areas of the most fertile land capable of supporting numerous
happy homes, but peopled only by a few wandering savages, it might be
argued that the struggle for existence had not been sufficiently severe to
force man upwards to his highest standard. Judging from all that we know
of man and the lower animals, there has always been sufficient variability
in their intellectual and moral faculties, for a steady advance through
natural selection. No doubt such advance demands many favourable
concurrent circumstances; but it may well be doubted whether the most
favourable would have sufficed, had not the rate of increase been rapid,
and the consequent struggle for existence extremely severe. It even
appears from what we see, for instance, in parts of S. America, that a
people which may be called civilised, such as the Spanish settlers, is
liable to become indolent and to retrograde, when the conditions of life
are very easy. With highly civilised nations continued progress depends in
a subordinate degree on natural selection; for such nations do not supplant
and exterminate one another as do savage tribes. Nevertheless the more
intelligent members within the same community will succeed better in the
long run than the inferior, and leave a more numerous progeny, and this is
a form of natural selection. The more efficient causes of progress seem to
consist of a good education during youth whilst the brain is impressible,
and of a high standard of excellence, inculcated by the ablest and best
men, embodied in the laws, customs and traditions of the nation, and
enforced by public opinion. It should, however, be borne in mind, that the
enforcement of public opinion depends on our appreciation of the
approbation and disapprobation of others; and this appreciation is founded
on our sympathy, which it can hardly be doubted was originally developed
through natural selection as one of the most important elements of the
social instincts. (31. I am much indebted to Mr. John Morley for some
good criticisms on this subject: see, also Broca, 'Les Selections,' 'Revue
d'Anthropologie,' 1872.)
ON THE EVIDENCE THAT ALL CIVILISED NATIONS WERE ONCE BARBAROUS.
The present subject has been treated in so full and admirable a manner by
Sir J. Lubbock (32. 'On the Origin of Civilisation,' 'Proceedings of the
Ethnological Society,' Nov. 26, 1867.), Mr. Tylor, Mr. M'Lennan, and
others, that I need here give only the briefest summary of their results.
The arguments recently advanced by the Duke of Argyll (33. 'Primeval Man,'
1869.) and formerly by Archbishop Whately, in favour of the belief that man
came into the world as a civilised being, and that all savages have since
undergone degradation, seem to me weak in comparison with those advanced on
the other side. Many nations, no doubt, have fallen away in civilisation,
and some may have lapsed into utter barbarism, though on this latter head I
have met with no evidence. The Fuegians were probably compelled by other
conquering hordes to settle in their inhospitable country, and they may
have become in consequence somewhat more degraded; but it would be
difficult to prove that they have fallen much below the Botocudos, who
inhabit the finest parts of Brazil.
The evidence that all civilised nations are the descendants of barbarians,
consists, on the one side, of clear traces of their former low condition in
still-existing customs, beliefs, language, etc.; and on the other side, of
proofs that savages are independently able to raise themselves a few steps
in the scale of civilisation, and have actually thus risen. The evidence
on the first head is extremely curious, but cannot be here given: I refer
to such cases as that of the art of enumeration, which, as Mr. Tylor
clearly shews by reference to the words still used in some places,
originated in counting the fingers, first of one hand and then of the
other, and lastly of the toes. We have traces of this in our own decimal
system, and in the Roman numerals, where, after the V, which is supposed to
be an abbreviated picture of a human hand, we pass on to VI, etc., when the
other hand no doubt was used. So again, "when we speak of three-score and
ten, we are counting by the vigesimal system, each score thus ideally made,
standing for 20--for 'one man' as a Mexican or Carib would put it." (34.
'Royal Institution of Great Britain,' March 15, 1867. Also, 'Researches
into the Early History of Mankind,' 1865.) According to a large and
increasing school of philologists, every language bears the marks of its
slow and gradual evolution. So it is with the art of writing, for letters
are rudiments of pictorial representations. It is hardly possible to read
Mr. M'Lennan's work (35. 'Primitive Marriage,' 1865. See, likewise, an
excellent article, evidently by the same author, in the 'North British
Review,' July 1869. Also, Mr. L.H. Morgan, 'A Conjectural Solution of the
Origin of the Class, System of Relationship,' in 'Proc. American Acad. of
Sciences,' vol. vii. Feb. 1868. Prof. Schaaffhausen ('Anthropolog.
Review,' Oct. 1869, p. 373) remarks on "the vestiges of human sacrifices
found both in Homer and the Old Testament.") and not admit that almost all
civilised nations still retain traces of such rude habits as the forcible
capture of wives. What ancient nation, as the same author asks, can be
named that was originally monogamous? The primitive idea of justice, as
shewn by the law of battle and other customs of which vestiges still
remain, was likewise most rude. Many existing superstitions are the
remnants of former false religious beliefs. The highest form of religion--
the grand idea of God hating sin and loving righteousness--was unknown
during primeval times.
Turning to the other kind of evidence: Sir J. Lubbock has shewn that some
savages have recently improved a little in some of their simpler arts.
From the extremely curious account which he gives of the weapons, tools,
and arts, in use amongst savages in various parts of the world, it cannot
be doubted that these have nearly all been independent discoveries,
excepting perhaps the art of making fire. (36. Sir J. Lubbock,
'Prehistoric Times,' 2nd edit. 1869, chaps. xv. and xvi. et passim. See
also the excellent 9th Chapter in Tylor's 'Early History of Mankind,' 2nd
edit., 1870.) The Australian boomerang is a good instance of one such
independent discovery. The Tahitians when first visited had advanced in
many respects beyond the inhabitants of most of the other Polynesian
islands. There are no just grounds for the belief that the high culture of
the native Peruvians and Mexicans was derived from abroad (37. Dr. F.
Muller has made some good remarks to this effect in the 'Reise der Novara:
Anthropolog. Theil,' Abtheil. iii. 1868, s. 127.); many native plants were
there cultivated, and a few native animals domesticated. We should bear in
mind that, judging from the small influence of most missionaries, a
wandering crew from some semi-civilised land, if washed to the shores of
America, would not have produced any marked effect on the natives, unless
they had already become somewhat advanced. Looking to a very remote period
in the history of the world, we find, to use Sir J. Lubbock's well-known
terms, a paleolithic and neolithic period; and no one will pretend that the
art of grinding rough flint tools was a borrowed one. In all parts of
Europe, as far east as Greece, in Palestine, India, Japan, New Zealand, and
Africa, including Egypt, flint tools have been discovered in abundance; and
of their use the existing inhabitants retain no tradition. There is also
indirect evidence of their former use by the Chinese and ancient Jews.
Hence there can hardly be a doubt that the inhabitants of these countries,
which include nearly the whole civilised world, were once in a barbarous
condition. To believe that man was aboriginally civilised and then
suffered utter degradation in so many regions, is to take a pitiably low
view of human nature. It is apparently a truer and more cheerful view that
progress has been much more general than retrogression; that man has risen,
though by slow and interrupted steps, from a lowly condition to the highest
standard as yet attained by him in knowledge, morals and religion.
CHAPTER VI.
ON THE AFFINITIES AND GENEALOGY OF MAN.
Position of man in the animal series--The natural system genealogical--
Adaptive characters of slight value--Various small points of resemblance
between man and the Quadrumana--Rank of man in the natural system--
Birthplace and antiquity of man--Absence of fossil connecting links--Lower
stages in the genealogy of man, as inferred, firstly from his affinities
and secondly from his structure--Early androgynous condition of the
Vertebrata--Conclusion.
Even if it be granted that the difference between man and his nearest
allies is as great in corporeal structure as some naturalists maintain, and
although we must grant that the difference between them is immense in
mental power, yet the facts given in the earlier chapters appear to
declare, in the plainest manner, that man is descended from some lower
form, notwithstanding that connecting-links have not hitherto been
discovered.
Man is liable to numerous, slight, and diversified variations, which are
induced by the same general causes, are governed and transmitted in
accordance with the same general laws, as in the lower animals. Man has
multiplied so rapidly, that he has necessarily been exposed to struggle for
existence, and consequently to natural selection. He has given rise to
many races, some of which differ so much from each other, that they have
often been ranked by naturalists as distinct species. His body is
constructed on the same homological plan as that of other mammals. He
passes through the same phases of embryological development. He retains
many rudimentary and useless structures, which no doubt were once
serviceable. Characters occasionally make their re-appearance in him,
which we have reason to believe were possessed by his early progenitors.
If the origin of man had been wholly different from that of all other
animals, these various appearances would be mere empty deceptions; but such
an admission is incredible. These appearances, on the other hand, are
intelligible, at least to a large extent, if man is the co-descendant with
other mammals of some unknown and lower form.
Some naturalists, from being deeply impressed with the mental and spiritual
powers of man, have divided the whole organic world into three kingdoms,
the Human, the Animal, and the Vegetable, thus giving to man a separate
kingdom. (1. Isidore Geoffroy St.-Hilaire gives a detailed account of the
position assigned to man by various naturalists in their classifications:
'Hist. Nat. Gen.' tom. ii. 1859, pp. 170-189.) Spiritual powers cannot be
compared or classed by the naturalist: but he may endeavour to shew, as I
have done, that the mental faculties of man and the lower animals do not
differ in kind, although immensely in degree. A difference in degree,
however great, does not justify us in placing man in a distinct kingdom, as
will perhaps be best illustrated by comparing the mental powers of two
insects, namely, a coccus or scale-insect and an ant, which undoubtedly
belong to the same class. The difference is here greater than, though of a
somewhat different kind from, that between man and the highest mammal. The
female coccus, whilst young, attaches itself by its proboscis to a plant;
sucks the sap, but never moves again; is fertilised and lays eggs; and this
is its whole history. On the other hand, to describe the habits and mental
powers of worker-ants, would require, as Pierre Huber has shewn, a large
volume; I may, however, briefly specify a few points. Ants certainly
communicate information to each other, and several unite for the same work,
or for games of play. They recognise their fellow-ants after months of
absence, and feel sympathy for each other. They build great edifices, keep
them clean, close the doors in the evening, and post sentries. They make
roads as well as tunnels under rivers, and temporary bridges over them, by
clinging together. They collect food for the community, and when an
object, too large for entrance, is brought to the nest, they enlarge the
door, and afterwards build it up again. They store up seeds, of which they
prevent the germination, and which, if damp, are brought up to the surface
to dry. They keep aphides and other insects as milch-cows. They go out to
battle in regular bands, and freely sacrifice their lives for the common
weal. They emigrate according to a preconcerted plan. They capture
slaves. They move the eggs of their aphides, as well as their own eggs and
cocoons, into warm parts of the nest, in order that they may be quickly
hatched; and endless similar facts could be given. (2. Some of the most
interesting facts ever published on the habits of ants are given by Mr.
Belt, in his 'Naturalist in Nicaragua,' 1874. See also Mr. Moggridge's
admirable work, 'Harvesting Ants,' etc., 1873, also 'L'Instinct chez les
Insectes,' by M. George Pouchet, 'Revue des Deux Mondes,' Feb. 1870, p.
682.) On the whole, the difference in mental power between an ant and a
coccus is immense; yet no one has ever dreamed of placing these insects in
distinct classes, much less in distinct kingdoms. No doubt the difference
is bridged over by other insects; and this is not the case with man and the
higher apes. But we have every reason to believe that the breaks in the
series are simply the results of many forms having become extinct.
Professor Owen, relying chiefly on the structure of the brain, has divided
the mammalian series into four sub-classes. One of these he devotes to
man; in another he places both the marsupials and the Monotremata; so that
he makes man as distinct from all other mammals as are these two latter
groups conjoined. This view has not been accepted, as far as I am aware,
by any naturalist capable of forming an independent judgment, and therefore
need not here be further considered.
We can understand why a classification founded on any single character or
organ--even an organ so wonderfully complex and important as the brain--or
on the high development of the mental faculties, is almost sure to prove
unsatisfactory. This principle has indeed been tried with hymenopterous
insects; but when thus classed by their habits or instincts, the
arrangement proved thoroughly artificial. (3. Westwood, 'Modern
Classification of Insects,' vol. ii. 1840, p. 87.) Classifications may, of
course, be based on any character whatever, as on size, colour, or the
element inhabited; but naturalists have long felt a profound conviction
that there is a natural system. This system, it is now generally admitted,
must be, as far as possible, genealogical in arrangement,--that is, the co-
descendants of the same form must be kept together in one group, apart from
the co-descendants of any other form; but if the parent-forms are related,
so will be their descendants, and the two groups together will form a
larger group. The amount of difference between the several groups--that is
the amount of modification which each has undergone--is expressed by such
terms as genera, families, orders, and classes. As we have no record of
the lines of descent, the pedigree can be discovered only by observing the
degrees of resemblance between the beings which are to be classed. For
this object numerous points of resemblance are of much more importance than
the amount of similarity or dissimilarity in a few points. If two
languages were found to resemble each other in a multitude of words and
points of construction, they would be universally recognised as having
sprung from a common source, notwithstanding that they differed greatly in
some few words or points of construction. But with organic beings the
points of resemblance must not consist of adaptations to similar habits of
life: two animals may, for instance, have had their whole frames modified
for living in the water, and yet they will not be brought any nearer to
each other in the natural system. Hence we can see how it is that
resemblances in several unimportant structures, in useless and rudimentary
organs, or not now functionally active, or in an embryological condition,
are by far the most serviceable for classification; for they can hardly be
due to adaptations within a late period; and thus they reveal the old lines
of descent or of true affinity.
We can further see why a great amount of modification in some one character
ought not to lead us to separate widely any two organisms. A part which
already differs much from the same part in other allied forms has already,
according to the theory of evolution, varied much; consequently it would
(as long as the organism remained exposed to the same exciting conditions)
be liable to further variations of the same kind; and these, if beneficial,
would be preserved, and thus be continually augmented. In many cases the
continued development of a part, for instance, of the beak of a bird, or of
the teeth of a mammal, would not aid the species in gaining its food, or
for any other object; but with man we can see no definite limit to the
continued development of the brain and mental faculties, as far as
advantage is concerned. Therefore in determining the position of man in
the natural or genealogical system, the extreme development of his brain
ought not to outweigh a multitude of resemblances in other less important
or quite unimportant points.
The greater number of naturalists who have taken into consideration the
whole structure of man, including his mental faculties, have followed
Blumenbach and Cuvier, and have placed man in a separate Order, under the
title of the Bimana, and therefore on an equality with the orders of the
Quadrumana, Carnivora, etc. Recently many of our best naturalists have
recurred to the view first propounded by Linnaeus, so remarkable for his
sagacity, and have placed man in the same Order with the Quadrumana, under
the title of the Primates. The justice of this conclusion will be
admitted: for in the first place, we must bear in mind the comparative
insignificance for classification of the great development of the brain in
man, and that the strongly-marked differences between the skulls of man and
the Quadrumana (lately insisted upon by Bischoff, Aeby, and others)
apparently follow from their differently developed brains. In the second
place, we must remember that nearly all the other and more important
differences between man and the Quadrumana are manifestly adaptive in their
nature, and relate chiefly to the erect position of man; such as the
structure of his hand, foot, and pelvis, the curvature of his spine, and
the position of his head. The family of Seals offers a good illustration
of the small importance of adaptive characters for classification. These
animals differ from all other Carnivora in the form of their bodies and in
the structure of their limbs, far more than does man from the higher apes;
yet in most systems, from that of Cuvier to the most recent one by Mr.
Flower (4. 'Proceedings Zoological Society,' 1863, p. 4.), seals are
ranked as a mere family in the Order of the Carnivora. If man had not been
his own classifier, he would never have thought of founding a separate
order for his own reception.
It would be beyond my limits, and quite beyond my knowledge, even to name
the innumerable points of structure in which man agrees with the other
Primates. Our great anatomist and philosopher, Prof. Huxley, has fully
discussed this subject (5. 'Evidence as to Man's Place in Nature,' 1863,
p. 70, et passim.), and concludes that man in all parts of his organization
differs less from the higher apes, than these do from the lower members of
the same group. Consequently there "is no justification for placing man in
a distinct order."
In an early part of this work I brought forward various facts, shewing how
closely man agrees in constitution with the higher mammals; and this
agreement must depend on our close similarity in minute structure and
chemical composition. I gave, as instances, our liability to the same
diseases, and to the attacks of allied parasites; our tastes in common for
the same stimulants, and the similar effects produced by them, as well as
by various drugs, and other such facts.
As small unimportant points of resemblance between man and the Quadrumana
are not commonly noticed in systematic works, and as, when numerous, they
clearly reveal our relationship, I will specify a few such points. The
relative position of our features is manifestly the same; and the various
emotions are displayed by nearly similar movements of the muscles and skin,
chiefly above the eyebrows and round the mouth. Some few expressions are,
indeed, almost the same, as in the weeping of certain kinds of monkeys and
in the laughing noise made by others, during which the corners of the mouth
are drawn backwards, and the lower eyelids wrinkled. The external ears are
curiously alike. In man the nose is much more prominent than in most
monkeys; but we may trace the commencement of an aquiline curvature in the
nose of the Hoolock Gibbon; and this in the Semnopithecus nasica is carried
to a ridiculous extreme.
The faces of many monkeys are ornamented with beards, whiskers, or
moustaches. The hair on the head grows to a great length in some species
of Semnopithecus (6. Isidore Geoffroy St.-Hilaire, 'Hist. Nat. Gen.' tom.
ii. 1859, p. 217.); and in the Bonnet monkey (Macacus radiatus) it radiates
from a point on the crown, with a parting down the middle. It is commonly
said that the forehead gives to man his noble and intellectual appearance;
but the thick hair on the head of the Bonnet monkey terminates downwards
abruptly, and is succeeded by hair so short and fine that at a little
distance the forehead, with the exception of the eyebrows, appears quite
naked. It has been erroneously asserted that eyebrows are not present in
any monkey. In the species just named the degree of nakedness of the
forehead differs in different individuals; and Eschricht states (7. 'Uber
die Richtung der Haare,' etc., Muller's 'Archiv fur Anat. und Phys.' 1837,
s. 51.) that in our children the limit between the hairy scalp and the
naked forehead is sometimes not well defined; so that here we seem to have
a trifling case of reversion to a progenitor, in whom the forehead had not
as yet become quite naked.
It is well known that the hair on our arms tends to converge from above and
below to a point at the elbow. This curious arrangement, so unlike that in
most of the lower mammals, is common to the gorilla, chimpanzee, orang,
some species of Hylobates, and even to some few American monkeys. But in
Hylobates agilis the hair on the fore-arm is directed downwards or towards
the wrist in the ordinary manner; and in H. lar it is nearly erect, with
only a very slight forward inclination; so that in this latter species it
is in a transitional state. It can hardly be doubted that with most
mammals the thickness of the hair on the back and its direction, is adapted
to throw off the rain; even the transverse hairs on the fore-legs of a dog
may serve for this end when he is coiled up asleep. Mr. Wallace, who has
carefully studied the habits of the orang, remarks that the convergence of
the hair towards the elbow on the arms of the orang may be explained as
serving to throw off the rain, for this animal during rainy weather sits
with its arms bent, and with the hands clasped round a branch or over its
head. According to Livingstone, the gorilla also "sits in pelting rain
with his hands over his head." (8. Quoted by Reade, 'The African Sketch
Book,' vol i. 1873, p. 152.) If the above explanation is correct, as seems
probable, the direction of the hair on our own arms offers a curious record
of our former state; for no one supposes that it is now of any use in
throwing off the rain; nor, in our present erect condition, is it properly
directed for this purpose.
It would, however, be rash to trust too much to the principle of adaptation
in regard to the direction of the hair in man or his early progenitors; for
it is impossible to study the figures given by Eschricht of the arrangement
of the hair on the human foetus (this being the same as in the adult) and
not agree with this excellent observer that other and more complex causes
have intervened. The points of convergence seem to stand in some relation
to those points in the embryo which are last closed in during development.
There appears, also, to exist some relation between the arrangement of the
hair on the limbs, and the course of the medullary arteries. (9. On the
hair in Hylobates, see 'Natural History of Mammals,' by C.L. Martin, 1841,
p. 415. Also, Isidore Geoffroy on the American monkeys and other kinds,
'Hist. Nat. Gen.' vol. ii. 1859, pp. 216, 243. Eschricht, ibid. s. 46, 55,
61. Owen, 'Anatomy of Vertebrates,' vol. iii. p. 619. Wallace,
'Contributions to the Theory of Natural Selection,' 1870, p. 344.)
It must not be supposed that the resemblances between man and certain apes
in the above and in many other points--such as in having a naked forehead,
long tresses on the head, etc.,--are all necessarily the result of unbroken
inheritance from a common progenitor, or of subsequent reversion. Many of
these resemblances are more probably due to analogous variation, which
follows, as I have elsewhere attempted to shew (10. 'Origin of Species,'
5th edit. 1869, p.194. 'The Variation of Animals and Plants under
Domestication,' vol. ii. 1868, p. 348.), from co-descended organisms having
a similar constitution, and having been acted on by like causes inducing
similar modifications. With respect to the similar direction of the hair
on the fore-arms of man and certain monkeys, as this character is common to
almost all the anthropomorphous apes, it may probably be attributed to
inheritance; but this is not certain, as some very distinct American
monkeys are thus characterised.
Although, as we have now seen, man has no just right to form a separate
Order for his own reception, he may perhaps claim a distinct Sub-order or
Family. Prof. Huxley, in his last work (11. 'An Introduction to the
Classification of Animals,' 1869, p. 99.), divides the primates into three
Sub-orders; namely, the Anthropidae with man alone, the Simiadae including
monkeys of all kinds, and the Lemuridae with the diversified genera of
lemurs. As far as differences in certain important points of structure are
concerned, man may no doubt rightly claim the rank of a Sub-order; and this
rank is too low, if we look chiefly to his mental faculties. Nevertheless,
from a genealogical point of view it appears that this rank is too high,
and that man ought to form merely a Family, or possibly even only a Sub-
family. If we imagine three lines of descent proceeding from a common
stock, it is quite conceivable that two of them might after the lapse of
ages be so slightly changed as still to remain as species of the same
genus, whilst the third line might become so greatly modified as to deserve
to rank as a distinct Sub-family, Family, or even Order. But in this case
it is almost certain that the third line would still retain through
inheritance numerous small points of resemblance with the other two. Here,
then, would occur the difficulty, at present insoluble, how much weight we
ought to assign in our classifications to strongly-marked differences in
some few points,--that is, to the amount of modification undergone; and how
much to close resemblance in numerous unimportant points, as indicating the
lines of descent or genealogy. To attach much weight to the few but strong
differences is the most obvious and perhaps the safest course, though it
appears more correct to pay great attention to the many small resemblances,
as giving a truly natural classification.
In forming a judgment on this head with reference to man, we must glance at
the classification of the Simiadae. This family is divided by almost all
naturalists into the Catarrhine group, or Old World monkeys, all of which
are characterised (as their name expresses) by the peculiar structure of
their nostrils, and by having four premolars in each jaw; and into the
Platyrrhine group or New World monkeys (including two very distinct sub-
groups), all of which are characterised by differently constructed
nostrils, and by having six premolars in each jaw. Some other small
differences might be mentioned. Now man unquestionably belongs in his
dentition, in the structure of his nostrils, and some other respects, to
the Catarrhine or Old World division; nor does he resemble the Platyrrhines
more closely than the Catarrhines in any characters, excepting in a few of
not much importance and apparently of an adaptive nature. It is therefore
against all probability that some New World species should have formerly
varied and produced a man-like creature, with all the distinctive
characters proper to the Old World division; losing at the same time all
its own distinctive characters. There can, consequently, hardly be a doubt
that man is an off-shoot from the Old World Simian stem; and that under a
genealogical point of view he must be classed with the Catarrhine division.
(12. This is nearly the same classification as that provisionally adopted
by Mr. St. George Mivart, ('Transactions, Philosophical Society," 1867, p.
300), who, after separating the Lemuridae, divides the remainder of the
Primates into the Hominidae, the Simiadae which answer to the Catarrhines,
the Cebidae, and the Hapalidae,--these two latter groups answering to the
Platyrrhines. Mr. Mivart still abides by the same view; see 'Nature,'
1871, p. 481.)
The anthropomorphous apes, namely the gorilla, chimpanzee, orang, and
hylobates, are by most naturalists separated from the other Old World
monkeys, as a distinct sub-group. I am aware that Gratiolet, relying on
the structure of the brain, does not admit the existence of this sub-group,
and no doubt it is a broken one. Thus the orang, as Mr. St. G. Mivart
remarks, "is one of the most peculiar and aberrant forms to be found in the
Order." (13. 'Transactions, Zoolog. Soc.' vol. vi. 1867, p. 214.) The
remaining non-anthropomorphous Old World monkeys, are again divided by some
naturalists into two or three smaller sub-groups; the genus Semnopithecus,
with its peculiar sacculated stomach, being the type of one sub-group. But
it appears from M. Gaudry's wonderful discoveries in Attica, that during
the Miocene period a form existed there, which connected Semnopithecus and
Macacus; and this probably illustrates the manner in which the other and
higher groups were once blended together.
If the anthropomorphous apes be admitted to form a natural sub-group, then
as man agrees with them, not only in all those characters which he
possesses in common with the whole Catarrhine group, but in other peculiar
characters, such as the absence of a tail and of callosities, and in
general appearance, we may infer that some ancient member of the
anthropomorphous sub-group gave birth to man. It is not probable that,
through the law of analogous variation, a member of one of the other lower
sub-groups should have given rise to a man-like creature, resembling the
higher anthropomorphous apes in so many respects. No doubt man, in
comparison with most of his allies, has undergone an extraordinary amount
of modification, chiefly in consequence of the great development of his
brain and his erect position; nevertheless, we should bear in mind that he
"is but one of several exceptional forms of Primates." (14. Mr. St. G.
Mivart, 'Transactions of the Philosophical Society,' 1867, p. 410.)
Every naturalist, who believes in the principle of evolution, will grant
that the two main divisions of the Simiadae, namely the Catarrhine and
Platyrrhine monkeys, with their sub-groups, have all proceeded from some
one extremely ancient progenitor. The early descendants of this
progenitor, before they had diverged to any considerable extent from each
other, would still have formed a single natural group; but some of the
species or incipient genera would have already begun to indicate by their
diverging characters the future distinctive marks of the Catarrhine and
Platyrrhine divisions. Hence the members of this supposed ancient group
would not have been so uniform in their dentition, or in the structure of
their nostrils, as are the existing Catarrhine monkeys in one way and the
Platyrrhines in another way, but would have resembled in this respect the
allied Lemuridae, which differ greatly from each other in the form of their
muzzles (15. Messrs. Murie and Mivart on the Lemuroidea, 'Transactions,
Zoological Society,' vol. vii, 1869, p. 5.), and to an extraordinary degree
in their dentition.
The Catarrhine and Platyrrhine monkeys agree in a multitude of characters,
as is shewn by their unquestionably belonging to one and the same Order.
The many characters which they possess in common can hardly have been
independently acquired by so many distinct species; so that these
characters must have been inherited. But a naturalist would undoubtedly
have ranked as an ape or a monkey, an ancient form which possessed many
characters common to the Catarrhine and Platyrrhine monkeys, other
characters in an intermediate condition, and some few, perhaps, distinct
from those now found in either group. And as man from a genealogical point
of view belongs to the Catarrhine or Old World stock, we must conclude,
however much the conclusion may revolt our pride, that our early
progenitors would have been properly thus designated. (16. Haeckel has
come to this same conclusion. See 'Uber die Entstehung des
Menschengeschlechts,' in Virchow's 'Sammlung. gemein. wissen. Vortrage,'
1868, s. 61. Also his 'Naturliche Schopfungsgeschicte,' 1868, in which he
gives in detail his views on the genealogy of man.) But we must not fall
into the error of supposing that the early progenitor of the whole Simian
stock, including man, was identical with, or even closely resembled, any
existing ape or monkey.
ON THE BIRTHPLACE AND ANTIQUITY OF MAN.
We are naturally led to enquire, where was the birthplace of man at that
stage of descent when our progenitors diverged from the Catarrhine stock?
The fact that they belonged to this stock clearly shews that they inhabited
the Old World; but not Australia nor any oceanic island, as we may infer
from the laws of geographical distribution. In each great region of the
world the living mammals are closely related to the extinct species of the
same region. It is therefore probable that Africa was formerly inhabited
by extinct apes closely allied to the gorilla and chimpanzee; and as these
two species are now man's nearest allies, it is somewhat more probable that
our early progenitors lived on the African continent than elsewhere. But
it is useless to speculate on this subject; for two or three
anthropomorphous apes, one the Dryopithecus (17. Dr. C. Forsyth Major,
'Sur les Singes fossiles trouves en Italie:' 'Soc. Ital. des Sc. Nat.' tom.
xv. 1872.) of Lartet, nearly as large as a man, and closely allied to
Hylobates, existed in Europe during the Miocene age; and since so remote a
period the earth has certainly undergone many great revolutions, and there
has been ample time for migration on the largest scale.
At the period and place, whenever and wherever it was, when man first lost
his hairy covering, he probably inhabited a hot country; a circumstance
favourable for the frugiferous diet on which, judging from analogy, he
subsisted. We are far from knowing how long ago it was when man first
diverged from the Catarrhine stock; but it may have occurred at an epoch as
remote as the Eocene period; for that the higher apes had diverged from the
lower apes as early as the Upper Miocene period is shewn by the existence
of the Dryopithecus. We are also quite ignorant at how rapid a rate
organisms, whether high or low in the scale, may be modified under
favourable circumstances; we know, however, that some have retained the
same form during an enormous lapse of time. From what we see going on
under domestication, we learn that some of the co-descendants of the same
species may be not at all, some a little, and some greatly changed, all
within the same period. Thus it may have been with man, who has undergone
a great amount of modification in certain characters in comparison with the
higher apes.
The great break in the organic chain between man and his nearest allies,
which cannot be bridged over by any extinct or living species, has often
been advanced as a grave objection to the belief that man is descended from
some lower form; but this objection will not appear of much weight to those
who, from general reasons, believe in the general principle of evolution.
Breaks often occur in all parts of the series, some being wide, sharp and
defined, others less so in various degrees; as between the orang and its
nearest allies--between the Tarsius and the other Lemuridae--between the
elephant, and in a more striking manner between the Ornithorhynchus or
Echidna, and all other mammals. But these breaks depend merely on the
number of related forms which have become extinct. At some future period,
not very distant as measured by centuries, the civilised races of man will
almost certainly exterminate, and replace, the savage races throughout the
world. At the same time the anthropomorphous apes, as Professor
Schaaffhausen has remarked (18. 'Anthropological Review,' April 1867, p.
236.), will no doubt be exterminated. The break between man and his
nearest allies will then be wider, for it will intervene between man in a
more civilised state, as we may hope, even than the Caucasian, and some ape
as low as a baboon, instead of as now between the negro or Australian and
the gorilla.
With respect to the absence of fossil remains, serving to connect man with
his ape-like progenitors, no one will lay much stress on this fact who
reads Sir C. Lyell's discussion (19. 'Elements of Geology,' 1865, pp. 583-
585. 'Antiquity of Man,' 1863, p. 145.), where he shews that in all the
vertebrate classes the discovery of fossil remains has been a very slow and
fortuitous process. Nor should it be forgotten that those regions which
are the most likely to afford remains connecting man with some extinct ape-
like creature, have not as yet been searched by geologists.
LOWER STAGES IN THE GENEALOGY OF MAN.
We have seen that man appears to have diverged from the Catarrhine or Old
World division of the Simiadae, after these had diverged from the New World
division. We will now endeavour to follow the remote traces of his
genealogy, trusting principally to the mutual affinities between the
various classes and orders, with some slight reference to the periods, as
far as ascertained, of their successive appearance on the earth. The
Lemuridae stand below and near to the Simiadae, and constitute a very
distinct family of the primates, or, according to Haeckel and others, a
distinct Order. This group is diversified and broken to an extraordinary
degree, and includes many aberrant forms. It has, therefore, probably
suffered much extinction. Most of the remnants survive on islands, such as
Madagascar and the Malayan archipelago, where they have not been exposed to
so severe a competition as they would have been on well-stocked continents.
This group likewise presents many gradations, leading, as Huxley remarks
(20. 'Man's Place in Nature,' p. 105.), "insensibly from the crown and
summit of the animal creation down to creatures from which there is but a
step, as it seems, to the lowest, smallest, and least intelligent of the
placental mammalia." From these various considerations it is probable that
the Simiadae were originally developed from the progenitors of the existing
Lemuridae; and these in their turn from forms standing very low in the
mammalian series.
The Marsupials stand in many important characters below the placental
mammals. They appeared at an earlier geological period, and their range
was formerly much more extensive than at present. Hence the Placentata are
generally supposed to have been derived from the Implacentata or
Marsupials; not, however, from forms closely resembling the existing
Marsupials, but from their early progenitors. The Monotremata are plainly
allied to the Marsupials, forming a third and still lower division in the
great mammalian series. They are represented at the present day solely by
the Ornithorhynchus and Echidna; and these two forms may be safely
considered as relics of a much larger group, representatives of which have
been preserved in Australia through some favourable concurrence of
circumstances. The Monotremata are eminently interesting, as leading in
several important points of structure towards the class of reptiles.
In attempting to trace the genealogy of the Mammalia, and therefore of man,
lower down in the series, we become involved in greater and greater
obscurity; but as a most capable judge, Mr. Parker, has remarked, we have
good reason to believe, that no true bird or reptile intervenes in the
direct line of descent. He who wishes to see what ingenuity and knowledge
can effect, may consult Prof. Haeckel's works. (21. Elaborate tables are
given in his 'Generelle Morphologie' (B. ii. s. cliii. and s. 425); and
with more especial reference to man in his 'Naturliche
Schopfungsgeschichte,' 1868. Prof. Huxley, in reviewing this latter work
('The Academy,' 1869, p. 42) says, that he considers the phylum or lines of
descent of the Vertebrata to be admirably discussed by Haeckel, although he
differs on some points. He expresses, also, his high estimate of the
general tenor and spirit of the whole work.) I will content myself with a
few general remarks. Every evolutionist will admit that the five great
vertebrate classes, namely, mammals, birds, reptiles, amphibians, and
fishes, are descended from some one prototype; for they have much in
common, especially during their embryonic state. As the class of fishes is
the most lowly organised, and appeared before the others, we may conclude
that all the members of the vertebrate kingdom are derived from some
fishlike animal. The belief that animals so distinct as a monkey, an
elephant, a humming-bird, a snake, a frog, and a fish, etc., could all have
sprung from the same parents, will appear monstrous to those who have not
attended to the recent progress of natural history. For this belief
implies the former existence of links binding closely together all these
forms, now so utterly unlike.
Nevertheless, it is certain that groups of animals have existed, or do now
exist, which serve to connect several of the great vertebrate classes more
or less closely. We have seen that the Ornithorhynchus graduates towards
reptiles; and Prof. Huxley has discovered, and is confirmed by Mr. Cope and
others, that the Dinosaurians are in many important characters intermediate
between certain reptiles and certain birds--the birds referred to being the
ostrich-tribe (itself evidently a widely-diffused remnant of a larger
group) and the Archeopteryx, that strange Secondary bird, with a long
lizard-like tail. Again, according to Prof. Owen (22. 'Palaeontology'
1860, p. 199.), the Ichthyosaurians--great sea-lizards furnished with
paddles--present many affinities with fishes, or rather, according to
Huxley, with amphibians; a class which, including in its highest division
frogs and toads, is plainly allied to the Ganoid fishes. These latter
fishes swarmed during the earlier geological periods, and were constructed
on what is called a generalised type, that is, they presented diversified
affinities with other groups of organisms. The Lepidosiren is also so
closely allied to amphibians and fishes, that naturalists long disputed in
which of these two classes to rank it; it, and also some few Ganoid fishes,
have been preserved from utter extinction by inhabiting rivers, which are
harbours of refuge, and are related to the great waters of the ocean in the
same way that islands are to continents.
Lastly, one single member of the immense and diversified class of fishes,
namely, the lancelet or amphioxus, is so different from all other fishes,
that Haeckel maintains that it ought to form a distinct class in the
vertebrate kingdom. This fish is remarkable for its negative characters;
it can hardly be said to possess a brain, vertebral column, or heart, etc.;
so that it was classed by the older naturalists amongst the worms. Many
years ago Prof. Goodsir perceived that the lancelet presented some
affinities with the Ascidians, which are invertebrate, hermaphrodite,
marine creatures permanently attached to a support. They hardly appear
like animals, and consist of a simple, tough, leathery sack, with two small
projecting orifices. They belong to the Mulluscoida of Huxley--a lower
division of the great kingdom of the Mollusca; but they have recently been
placed by some naturalists amongst the Vermes or worms. Their larvae
somewhat resemble tadpoles in shape (23. At the Falkland Islands I had the
satisfaction of seeing, in April, 1833, and therefore some years before any
other naturalist, the locomotive larvae of a compound Ascidian, closely
allied to Synoicum, but apparently generically distinct from it. The tail
was about five times as long as the oblong head, and terminated in a very
fine filament. It was, as sketched by me under a simple microscope,
plainly divided by transverse opaque partitions, which I presume represent
the great cells figured by Kovalevsky. At an early stage of development
the tail was closely coiled round the head of the larva.), and have the
power of swimming freely about. Mr. Kovalevsky (24. 'Memoires de l'Acad.
des Sciences de St. Petersbourg,' tom. x. No. 15, 1866.) has lately
observed that the larvae of Ascidians are related to the Vertebrata, in
their manner of development, in the relative position of the nervous
system, and in possessing a structure closely like the chorda dorsalis of
vertebrate animals; and in this he has been since confirmed by Prof.
Kupffer. M. Kovalevsky writes to me from Naples, that he has now carried
these observations yet further, and should his results be well established,
the whole will form a discovery of the very greatest value. Thus, if we
may rely on embryology, ever the safest guide in classification, it seems
that we have at last gained a clue to the source whence the Vertebrata were
derived. (25. But I am bound to add that some competent judges dispute
this conclusion; for instance, M. Giard, in a series of papers in the
'Archives de Zoologie Experimentale,' for 1872. Nevertheless, this
naturalist remarks, p. 281, "L'organisation de la larve ascidienne en
dehors de toute hypothese et de toute theorie, nous montre comment la
nature peut produire la disposition fondamentale du type vertebre
(l'existence d'une corde dorsale) chez un invertebre par la seule condition
vitale de l'adaptation, et cette simple possibilite du passage supprime
l'abime entre les deux sous-regnes, encore bien qu'en ignore par ou le
passage s'est fait en realite.") We should then be justified in believing
that at an extremely remote period a group of animals existed, resembling
in many respects the larvae of our present Ascidians, which diverged into
two great branches--the one retrograding in development and producing the
present class of Ascidians, the other rising to the crown and summit of the
animal kingdom by giving birth to the Vertebrata.
We have thus far endeavoured rudely to trace the genealogy of the
Vertebrata by the aid of their mutual affinities. We will now look to man
as he exists; and we shall, I think, be able partially to restore the
structure of our early progenitors, during successive periods, but not in
due order of time. This, can be effected by means of the rudiments which
man still retains, by the characters which occasionally make their
appearance in him through reversion, and by the aid of the principles of
morphology and embryology. The various facts, to which I shall here
allude, have been given in the previous chapters.
The early progenitors of man must have been once covered with hair, both
sexes having beards; their ears were probably pointed, and capable of
movement; and their bodies were provided with a tail, having the proper
muscles. Their limbs and bodies were also acted on by many muscles which
now only occasionally reappear, but are normally present in the Quadrumana.
At this or some earlier period, the great artery and nerve of the humerus
ran through a supra-condyloid foramen. The intestine gave forth a much
larger diverticulum or caecum than that now existing. The foot was then
prehensile, judging from the condition of the great toe in the foetus; and
our progenitors, no doubt, were arboreal in their habits, and frequented
some warm, forest-clad land. The males had great canine teeth, which
served them as formidable weapons. At a much earlier period the uterus was
double; the excreta were voided through a cloaca; and the eye was protected
by a third eyelid or nictitating membrane. At a still earlier period the
progenitors of man must have been aquatic in their habits; for morphology
plainly tells us that our lungs consist of a modified swim-bladder, which
once served as a float. The clefts on the neck in the embryo of man shew
where the branchiae once existed. In the lunar or weekly recurrent periods
of some of our functions we apparently still retain traces of our
primordial birthplace, a shore washed by the tides. At about this same
early period the true kidneys were replaced by the corpora wolffiana. The
heart existed as a simple pulsating vessel; and the chorda dorsalis took
the place of a vertebral column. These early ancestors of man, thus seen
in the dim recesses of time, must have been as simply, or even still more
simply organised than the lancelet or amphioxus.
There is one other point deserving a fuller notice. It has long been known
that in the vertebrate kingdom one sex bears rudiments of various accessory
parts, appertaining to the reproductive system, which properly belong to
the opposite sex; and it has now been ascertained that at a very early
embryonic period both sexes possess true male and female glands. Hence
some remote progenitor of the whole vertebrate kingdom appears to have been
hermaphrodite or androgynous. (26. This is the conclusion of Prof.
Gegenbaur, one of the highest authorities in comparative anatomy: see
'Grundzuge der vergleich. Anat.' 1870, s. 876. The result has been arrived
at chiefly from the study of the Amphibia; but it appears from the
researches of Waldeyer (as quoted in 'Journal of Anat. and Phys.' 1869, p.
161), that the sexual organs of even "the higher vertebrata are, in their
early condition, hermaphrodite." Similar views have long been held by some
authors, though until recently without a firm basis.) But here we
encounter a singular difficulty. In the mammalian class the males possess
rudiments of a uterus with the adjacent passage, in their vesiculae
prostaticae; they bear also rudiments of mammae, and some male Marsupials
have traces of a marsupial sack. (27. The male Thylacinus offers the best
instance. Owen, 'Anatomy of Vertebrates,' vol. iii. p. 771.) Other
analogous facts could be added. Are we, then, to suppose that some
extremely ancient mammal continued androgynous, after it had acquired the
chief distinctions of its class, and therefore after it had diverged from
the lower classes of the vertebrate kingdom? This seems very improbable,
for we have to look to fishes, the lowest of all the classes, to find any
still existent androgynous forms. (28. Hermaphroditism has been observed
in several species of Serranus, as well as in some other fishes, where it
is either normal and symmetrical, or abnormal and unilateral. Dr.
Zouteveen has given me references on this subject, more especially to a
paper by Prof. Halbertsma, in the 'Transact. of the Dutch Acad. of
Sciences,' vol. xvi. Dr. Gunther doubts the fact, but it has now been
recorded by too many good observers to be any longer disputed. Dr. M.
Lessona writes to me, that he has verified the observations made by
Cavolini on Serranus. Prof. Ercolani has recently shewn ('Accad. delle
Scienze,' Bologna, Dec. 28, 1871) that eels are androgynous.) That various
accessory parts, proper to each sex, are found in a rudimentary condition
in the opposite sex, may be explained by such organs having been gradually
acquired by the one sex, and then transmitted in a more or less imperfect
state to the other. When we treat of sexual selection, we shall meet with
innumerable instances of this form of transmission,--as in the case of the
spurs, plumes, and brilliant colours, acquired for battle or ornament by
male birds, and inherited by the females in an imperfect or rudimentary
condition.
The possession by male mammals of functionally imperfect mammary organs is,
in some respects, especially curious. The Monotremata have the proper
milk-secreting glands with orifices, but no nipples; and as these animals
stand at the very base of the mammalian series, it is probable that the
progenitors of the class also had milk-secreting glands, but no nipples.
This conclusion is supported by what is known of their manner of
development; for Professor Turner informs me, on the authority of Kolliker
and Langer, that in the embryo the mammary glands can be distinctly traced
before the nipples are in the least visible; and the development of
successive parts in the individual generally represents and accords with
the development of successive beings in the same line of descent. The
Marsupials differ from the Monotremata by possessing nipples; so that
probably these organs were first acquired by the Marsupials, after they had
diverged from, and risen above, the Monotremata, and were then transmitted
to the placental mammals. (29. Prof. Gegenbaur has shewn ('Jenaische
Zeitschrift,' Bd. vii. p. 212) that two distinct types of nipples prevail
throughout the several mammalian orders, but that it is quite intelligible
how both could have been derived from the nipples of the Marsupials, and
the latter from those of the Monotremata. See, also, a memoir by Dr. Max
Huss, on the mammary glands, ibid. B. viii. p. 176.) No one will suppose
that the marsupials still remained androgynous, after they had
approximately acquired their present structure. How then are we to account
for male mammals possessing mammae? It is possible that they were first
developed in the females and then transferred to the males, but from what
follows this is hardly probable.
It may be suggested, as another view, that long after the progenitors of
the whole mammalian class had ceased to be androgynous, both sexes yielded
milk, and thus nourished their young; and in the case of the Marsupials,
that both sexes carried their young in marsupial sacks. This will not
appear altogether improbable, if we reflect that the males of existing
syngnathous fishes receive the eggs of the females in their abdominal
pouches, hatch them, and afterwards, as some believe, nourish the young
(30. Mr. Lockwood believes (as quoted in 'Quart. Journal of Science,'
April 1868, p. 269), from what he has observed of the development of
Hippocampus, that the walls of the abdominal pouch of the male in some way
afford nourishment. On male fishes hatching the ova in their mouths, see a
very interesting paper by Prof. Wyman, in 'Proc. Boston Soc. of Nat. Hist.'
Sept. 15, 1857; also Prof. Turner, in 'Journal of Anatomy and Physiology,'
Nov. 1, 1866, p. 78. Dr. Gunther has likewise described similar cases.);--
that certain other male fishes hatch the eggs within their mouths or
branchial cavities;--that certain male toads take the chaplets of eggs from
the females, and wind them round their own thighs, keeping them there until
the tadpoles are born;--that certain male birds undertake the whole duty of
incubation, and that male pigeons, as well as the females, feed their
nestlings with a secretion from their crops. But the above suggestion
first occurred to me from mammary glands of male mammals being so much more
perfectly developed than the rudiments of the other accessory reproductive
parts, which are found in the one sex though proper to the other. The
mammary glands and nipples, as they exist in male mammals, can indeed
hardly be called rudimentary; they are merely not fully developed, and not
functionally active. They are sympathetically affected under the influence
of certain diseases, like the same organs in the female. They often
secrete a few drops of milk at birth and at puberty: this latter fact
occurred in the curious case, before referred to, where a young man
possessed two pairs of mammae. In man and some other male mammals these
organs have been known occasionally to become so well developed during
maturity as to yield a fair supply of milk. Now if we suppose that during
a former prolonged period male mammals aided the females in nursing their
offspring (31. Mlle. C. Royer has suggested a similar view in her 'Origine
de l'homme,' etc., 1870.), and that afterwards from some cause (as from the
production of a smaller number of young) the males ceased to give this aid,
disuse of the organs during maturity would lead to their becoming inactive;
and from two well-known principles of inheritance, this state of inactivity
would probably be transmitted to the males at the corresponding age of
maturity. But at an earlier age these organs would be left unaffected, so
that they would be almost equally well developed in the young of both
sexes.
CONCLUSION.
Von Baer has defined advancement or progress in the organic scale better
than any one else, as resting on the amount of differentiation and
specialisation of the several parts of a being,--when arrived at maturity,
as I should be inclined to add. Now as organisms have become slowly
adapted to diversified lines of life by means of natural selection, their
parts will have become more and more differentiated and specialised for
various functions from the advantage gained by the division of
physiological labour. The same part appears often to have been modified
first for one purpose, and then long afterwards for some other and quite
distinct purpose; and thus all the parts are rendered more and more
complex. But each organism still retains the general type of structure of
the progenitor from which it was aboriginally derived. In accordance with
this view it seems, if we turn to geological evidence, that organisation on
the whole has advanced throughout the world by slow and interrupted steps.
In the great kingdom of the Vertebrata it has culminated in man. It must
not, however, be supposed that groups of organic beings are always
supplanted, and disappear as soon as they have given birth to other and
more perfect groups. The latter, though victorious over their
predecessors, may not have become better adapted for all places in the
economy of nature. Some old forms appear to have survived from inhabiting
protected sites, where they have not been exposed to very severe
competition; and these often aid us in constructing our genealogies, by
giving us a fair idea of former and lost populations. But we must not fall
into the error of looking at the existing members of any lowly-organised
group as perfect representatives of their ancient predecessors.
The most ancient progenitors in the kingdom of the Vertebrata, at which we
are able to obtain an obscure glance, apparently consisted of a group of
marine animals (32. The inhabitants of the seashore must be greatly
affected by the tides; animals living either about the MEAN high-water
mark, or about the MEAN low-water mark, pass through a complete cycle of
tidal changes in a fortnight. Consequently, their food supply will undergo
marked changes week by week. The vital functions of such animals, living
under these conditions for many generations, can hardly fail to run their
course in regular weekly periods. Now it is a mysterious fact that in the
higher and now terrestrial Vertebrata, as well as in other classes, many
normal and abnormal processes have one or more whole weeks as their
periods; this would be rendered intelligible if the Vertebrata are
descended from an animal allied to the existing tidal Ascidians. Many
instances of such periodic processes might be given, as the gestation of
mammals, the duration of fevers, etc. The hatching of eggs affords also a
good example, for, according to Mr. Bartlett ('Land and Water,' Jan. 7,
1871), the eggs of the pigeon are hatched in two weeks; those of the fowl
in three; those of the duck in four; those of the goose in five; and those
of the ostrich in seven weeks. As far as we can judge, a recurrent period,
if approximately of the right duration for any process or function, would
not, when once gained, be liable to change; consequently it might be thus
transmitted through almost any number of generations. But if the function
changed, the period would have to change, and would be apt to change almost
abruptly by a whole week. This conclusion, if sound, is highly remarkable;
for the period of gestation in each mammal, and the hatching of each bird's
eggs, and many other vital processes, thus betray to us the primordial
birthplace of these animals.), resembling the larvae of existing Ascidians.
These animals probably gave rise to a group of fishes, as lowly organised
as the lancelet; and from these the Ganoids, and other fishes like the
Lepidosiren, must have been developed. From such fish a very small advance
would carry us on to the Amphibians. We have seen that birds and reptiles
were once intimately connected together; and the Monotremata now connect
mammals with reptiles in a slight degree. But no one can at present say by
what line of descent the three higher and related classes, namely, mammals,
birds, and reptiles, were derived from the two lower vertebrate classes,
namely, amphibians and fishes. In the class of mammals the steps are not
difficult to conceive which led from the ancient Monotremata to the ancient
Marsupials; and from these to the early progenitors of the placental
mammals. We may thus ascend to the Lemuridae; and the interval is not very
wide from these to the Simiadae. The Simiadae then branched off into two
great stems, the New World and Old World monkeys; and from the latter, at a
remote period, Man, the wonder and glory of the Universe, proceeded.
Thus we have given to man a pedigree of prodigious length, but not, it may
be said, of noble quality. The world, it has often been remarked, appears
as if it had long been preparing for the advent of man: and this, in one
sense is strictly true, for he owes his birth to a long line of
progenitors. If any single link in this chain had never existed, man would
not have been exactly what he now is. Unless we wilfully close our eyes,
we may, with our present knowledge, approximately recognise our parentage;
nor need we feel ashamed of it. The most humble organism is something much
higher than the inorganic dust under our feet; and no one with an unbiassed
mind can study any living creature, however humble, without being struck
with enthusiasm at its marvellous structure and properties.
CHAPTER VII.
ON THE RACES OF MAN.
The nature and value of specific characters--Application to the races of
man--Arguments in favour of, and opposed to, ranking the so-called races of
man as district species--Sub-species--Monogenists and polygenists--
Convergence of character--Numerous points of resemblance in body and mind
between the most distinct races of man--The state of man when he first
spread over the earth--Each race not descended from a single pair--The
extinction of races--The formation of races--The effects of crossing--
Slight influence of the direct action of the conditions of life--Slight or
no influence of natural selection--Sexual selection.
It is not my intention here to describe the several so-called races of men;
but I am about to enquire what is the value of the differences between them
under a classificatory point of view, and how they have originated. In
determining whether two or more allied forms ought to be ranked as species
or varieties, naturalists are practically guided by the following
considerations; namely, the amount of difference between them, and whether
such differences relate to few or many points of structure, and whether
they are of physiological importance; but more especially whether they are
constant. Constancy of character is what is chiefly valued and sought for
by naturalists. Whenever it can be shewn, or rendered probable, that the
forms in question have remained distinct for a long period, this becomes an
argument of much weight in favour of treating them as species. Even a
slight degree of sterility between any two forms when first crossed, or in
their offspring, is generally considered as a decisive test of their
specific distinctness; and their continued persistence without blending
within the same area, is usually accepted as sufficient evidence, either of
some degree of mutual sterility, or in the case of animals of some mutual
repugnance to pairing.
Independently of fusion from intercrossing, the complete absence, in a
well-investigated region, of varieties linking together any two closely-
allied forms, is probably the most important of all the criterions of their
specific distinctness; and this is a somewhat different consideration from
mere constancy of character, for two forms may be highly variable and yet
not yield intermediate varieties. Geographical distribution is often
brought into play unconsciously and sometimes consciously; so that forms
living in two widely separated areas, in which most of the other
inhabitants are specifically distinct, are themselves usually looked at as
distinct; but in truth this affords no aid in distinguishing geographical
races from so-called good or true species.
Now let us apply these generally-admitted principles to the races of man,
viewing him in the same spirit as a naturalist would any other animal. In
regard to the amount of difference between the races, we must make some
allowance for our nice powers of discrimination gained by the long habit of
observing ourselves. In India, as Elphinstone remarks, although a newly-
arrived European cannot at first distinguish the various native races, yet
they soon appear to him extremely dissimilar (1. 'History of India,' 1841,
vol. i. p. 323. Father Ripa makes exactly the same remark with respect to
the Chinese.); and the Hindoo cannot at first perceive any difference
between the several European nations. Even the most distinct races of man
are much more like each other in form than would at first be supposed;
certain negro tribes must be excepted, whilst others, as Dr. Rohlfs writes
to me, and as I have myself seen, have Caucasian features. This general
similarity is well shewn by the French photographs in the Collection
Anthropologique du Museum de Paris of the men belonging to various races,
the greater number of which might pass for Europeans, as many persons to
whom I have shewn them have remarked. Nevertheless, these men, if seen
alive, would undoubtedly appear very distinct, so that we are clearly much
influenced in our judgment by the mere colour of the skin and hair, by
slight differences in the features, and by expression.
There is, however, no doubt that the various races, when carefully compared
and measured, differ much from each other,--as in the texture of the hair,
the relative proportions of all parts of the body (2. A vast number of
measurements of Whites, Blacks, and Indians, are given in the
'Investigations in the Military and Anthropolog. Statistics of American
Soldiers,' by B.A. Gould, 1869, pp. 298-358; 'On the capacity of the
lungs,' p. 471. See also the numerous and valuable tables, by Dr.
Weisbach, from the observations of Dr. Scherzer and Dr. Schwarz, in the
'Reise der Novara: Anthropolog. Theil,' 1867.), the capacity of the lungs,
the form and capacity of the skull, and even in the convolutions of the
brain. (3. See, for instance, Mr. Marshall's account of the brain of a
Bushwoman, in 'Philosophical Transactions,' 1864, p. 519.) But it would be
an endless task to specify the numerous points of difference. The races
differ also in constitution, in acclimatisation and in liability to certain
diseases. Their mental characteristics are likewise very distinct; chiefly
as it would appear in their emotional, but partly in their intellectual
faculties. Every one who has had the opportunity of comparison, must have
been struck with the contrast between the taciturn, even morose, aborigines
of S. America and the light-hearted, talkative negroes. There is a nearly
similar contrast between the Malays and the Papuans (4. Wallace, 'The
Malay Archipelago,' vol. ii. 1869, p. 178.), who live under the same
physical conditions, and are separated from each other only by a narrow
space of sea.
We will first consider the arguments which may be advanced in favour of
classing the races of man as distinct species, and then the arguments on
the other side. If a naturalist, who had never before seen a Negro,
Hottentot, Australian, or Mongolian, were to compare them, he would at once
perceive that they differed in a multitude of characters, some of slight
and some of considerable importance. On enquiry he would find that they
were adapted to live under widely different climates, and that they
differed somewhat in bodily constitution and mental disposition. If he
were then told that hundreds of similar specimens could be brought from the
same countries, he would assuredly declare that they were as good species
as many to which he had been in the habit of affixing specific names. This
conclusion would be greatly strengthened as soon as he had ascertained that
these forms had all retained the same character for many centuries; and
that negroes, apparently identical with existing negroes, had lived at
least 4000 years ago. (5. With respect to the figures in the famous
Egyptian caves of Abou-Simbel, M. Pouchet says ('The Plurality of the Human
Races,' Eng. translat., 1864, p. 50), that he was far from finding
recognisable representations of the dozen or more nations which some
authors believe that they can recognise. Even some of the most strongly-
marked races cannot be identified with that degree of unanimity which might
have been expected from what has been written on the subject. Thus Messrs.
Nott and Gliddon ('Types of Mankind,' p. 148), state that Rameses II., or
the Great, has features superbly European; whereas Knox, another firm
believer in the specific distinctness of the races of man ('Races of Man,'
1850, p. 201), speaking of young Memnon (the same as Rameses II., as I am
informed by Mr. Birch), insists in the strongest manner that he is
identical in character with the Jews of Antwerp. Again, when I looked at
the statue of Amunoph III., I agreed with two officers of the
establishment, both competent judges, that he had a strongly-marked negro
type of features; but Messrs. Nott and Gliddon (ibid. p. 146, fig. 53),
describe him as a hybrid, but not of "negro intermixture.") He would also
hear, on the authority of an excellent observer, Dr. Lund (6. As quoted by
Nott and Gliddon, 'Types of Mankind,' 1854, p. 439. They give also
corroborative evidence; but C. Vogt thinks that the subject requires
further investigation.), that the human skulls found in the caves of
Brazil, entombed with many extinct mammals, belonged to the same type as
that now prevailing throughout the American Continent.
Our naturalist would then perhaps turn to geographical distribution, and he
would probably declare that those forms must be distinct species, which
differ not only in appearance, but are fitted for hot, as well as damp or
dry countries, and for the Artic regions. He might appeal to the fact that
no species in the group next to man--namely, the Quadrumana, can resist a
low temperature, or any considerable change of climate; and that the
species which come nearest to man have never been reared to maturity, even
under the temperate climate of Europe. He would be deeply impressed with
the fact, first noticed by Agassiz (7. 'Diversity of Origin of the Human
Races,' in the 'Christian Examiner,' July 1850.), that the different races
of man are distributed over the world in the same zoological provinces, as
those inhabited by undoubtedly distinct species and genera of mammals.
This is manifestly the case with the Australian, Mongolian, and Negro races
of man; in a less well-marked manner with the Hottentots; but plainly with
the Papuans and Malays, who are separated, as Mr. Wallace has shewn, by
nearly the same line which divides the great Malayan and Australian
zoological provinces. The Aborigines of America range throughout the
Continent; and this at first appears opposed to the above rule, for most of
the productions of the Southern and Northern halves differ widely: yet
some few living forms, as the opossum, range from the one into the other,
as did formerly some of the gigantic Edentata. The Esquimaux, like other
Arctic animals, extend round the whole polar regions. It should be
observed that the amount of difference between the mammals of the several
zoological provinces does not correspond with the degree of separation
between the latter; so that it can hardly be considered as an anomaly that
the Negro differs more, and the American much less from the other races of
man, than do the mammals of the African and American continents from the
mammals of the other provinces. Man, it may be added, does not appear to
have aboriginally inhabited any oceanic island; and in this respect, he
resembles the other members of his class.
In determining whether the supposed varieties of the same kind of domestic
animal should be ranked as such, or as specifically distinct, that is,
whether any of them are descended from distinct wild species, every
naturalist would lay much stress on the fact of their external parasites
being specifically distinct. All the more stress would be laid on this
fact, as it would be an exceptional one; for I am informed by Mr. Denny
that the most different kinds of dogs, fowls, and pigeons, in England, are
infested by the same species of Pediculi or lice. Now Mr. A. Murray has
carefully examined the Pediculi collected in different countries from the
different races of man (8. 'Transactions of the Royal Society of
Edinburgh,' vol. xxii, 1861, p. 567.); and he finds that they differ, not
only in colour, but in the structure of their claws and limbs. In every
case in which many specimens were obtained the differences were constant.
The surgeon of a whaling ship in the Pacific assured me that when the
Pediculi, with which some Sandwich Islanders on board swarmed, strayed on
to the bodies of the English sailors, they died in the course of three or
four days. These Pediculi were darker coloured, and appeared different
from those proper to the natives of Chiloe in South America, of which he
gave me specimens. These, again, appeared larger and much softer than
European lice. Mr. Murray procured four kinds from Africa, namely, from
the Negroes of the Eastern and Western coasts, from the Hottentots and
Kaffirs; two kinds from the natives of Australia; two from North and two
from South America. In these latter cases it may be presumed that the
Pediculi came from natives inhabiting different districts. With insects
slight structural differences, if constant, are generally esteemed of
specific value: and the fact of the races of man being infested by
parasites, which appear to be specifically distinct, might fairly be urged
as an argument that the races themselves ought to be classed as distinct
species.
Our supposed naturalist having proceeded thus far in his investigation,
would next enquire whether the races of men, when crossed, were in any
degree sterile. He might consult the work (9. 'On the Phenomena of
Hybridity in the Genus Homo,' Eng. translat., 1864.) of Professor Broca, a
cautious and philosophical observer, and in this he would find good
evidence that some races were quite fertile together, but evidence of an
opposite nature in regard to other races. Thus it has been asserted that
the native women of Australia and Tasmania rarely produce children to
European men; the evidence, however, on this head has now been shewn to be
almost valueless. The half-castes are killed by the pure blacks: and an
account has lately been published of eleven half-caste youths murdered and
burnt at the same time, whose remains were found by the police. (10. See
the interesting letter by Mr. T.A. Murray, in the 'Anthropological Review,'
April 1868, p. liii. In this letter Count Strzelecki's statement that
Australian women who have borne children to a white man, are afterwards
sterile with their own race, is disproved. M. A. de Quatrefages has also
collected (Revue des Cours Scientifiques, March, 1869, p. 239), much
evidence that Australians and Europeans are not sterile when crossed.)
Again, it has often been said that when mulattoes intermarry, they produce
few children; on the other hand, Dr. Bachman, of Charleston (11. 'An
Examination of Prof. Agassiz's Sketch of the Nat. Provinces of the Animal
World,' Charleston, 1855, p. 44.), positively asserts that he has known
mulatto families which have intermarried for several generations, and have
continued on an average as fertile as either pure whites or pure blacks.
Enquiries formerly made by Sir C. Lyell on this subject led him, as he
informs me, to the same conclusion. (12. Dr. Rohlfs writes to me that he
found the mixed races in the Great Sahara, derived from Arabs, Berbers, and
Negroes of three tribes, extraordinarily fertile. On the other hand, Mr.
Winwood Reade informs me that the Negroes on the Gold Coast, though
admiring white men and mulattoes, have a maxim that mulattoes should not
intermarry, as the children are few and sickly. This belief, as Mr. Reade
remarks, deserves attention, as white men have visited and resided on the
Gold Coast for four hundred years, so that the natives have had ample time
to gain knowledge through experience.) In the United States the census for
the year 1854 included, according to Dr. Bachman, 405,751 mulattoes; and
this number, considering all the circumstances of the case, seems small;
but it may partly be accounted for by the degraded and anomalous position
of the class, and by the profligacy of the women. A certain amount of
absorption of mulattoes into negroes must always be in progress; and this
would lead to an apparent diminution of the former. The inferior vitality
of mulattoes is spoken of in a trustworthy work (13. 'Military and
Anthropological Statistics of American Soldiers,' by B.A. Gould, 1869, p.
319.) as a well-known phenomenon; and this, although a different
consideration from their lessened fertility, may perhaps be advanced as a
proof of the specific distinctness of the parent races. No doubt both
animal and vegetable hybrids, when produced from extremely distinct
species, are liable to premature death; but the parents of mulattoes cannot
be put under the category of extremely distinct species. The common Mule,
so notorious for long life and vigour, and yet so sterile, shews how little
necessary connection there is in hybrids between lessened fertility and
vitality; other analogous cases could be cited.
Even if it should hereafter be proved that all the races of men were
perfectly fertile together, he who was inclined from other reasons to rank
them as distinct species, might with justice argue that fertility and
sterility are not safe criterions of specific distinctness. We know that
these qualities are easily affected by changed conditions of life, or by
close inter-breeding, and that they are governed by highly complex laws,
for instance, that of the unequal fertility of converse crosses between the
same two species. With forms which must be ranked as undoubted species, a
perfect series exists from those which are absolutely sterile when crossed,
to those which are almost or completely fertile. The degrees of sterility
do not coincide strictly with the degrees of difference between the parents
in external structure or habits of life. Man in many respects may be
compared with those animals which have long been domesticated, and a large
body of evidence can be advanced in favour of the Pallasian doctrine (14.
The 'Variation of Animals and Plants under Domestication,' vol. ii. p. 109.
I may here remind the reader that the sterility of species when crossed is
not a specially-acquired quality, but, like the incapacity of certain trees
to be grafted together, is incidental on other acquired differences. The
nature of these differences is unknown, but they relate more especially to
the reproductive system, and much less so to external structure or to
ordinary differences in constitution. One important element in the
sterility of crossed species apparently lies in one or both having been
long habituated to fixed conditions; for we know that changed conditions
have a special influence on the reproductive system, and we have good
reason to believe (as before remarked) that the fluctuating conditions of
domestication tend to eliminate that sterility which is so general with
species, in a natural state, when crossed. It has elsewhere been shewn by
me (ibid. vol. ii. p. 185, and 'Origin of Species,' 5th edit. p. 317), that
the sterility of crossed species has not been acquired through natural
selection: we can see that when two forms have already been rendered very
sterile, it is scarcely possible that their sterility should be augmented
by the preservation or survival of the more and more sterile individuals;
for, as the sterility increases, fewer and fewer offspring will be produced
from which to breed, and at last only single individuals will be produced
at the rarest intervals. But there is even a higher grade of sterility
than this. Both Gartner and Kolreuter have proved that in genera of
plants, including many species, a series can be formed from species which,
when crossed, yield fewer and fewer seeds, to species which never produce a
single seed, but yet are affected by the pollen of the other species, as
shewn by the swelling of the germen. It is here manifestly impossible to
select the more sterile individuals, which have already ceased to yield
seeds; so that the acme of sterility, when the germen alone is affected,
cannot have been gained through selection. This acme, and no doubt the
other grades of sterility, are the incidental results of certain unknown
differences in the constitution of the reproductive system of the species
which are crossed.), that domestication tends to eliminate the sterility
which is so general a result of the crossing of species in a state of
nature. From these several considerations, it may be justly urged that the
perfect fertility of the intercrossed races of man, if established, would
not absolutely preclude us from ranking them as distinct species.
Independently of fertility, the characters presented by the offspring from
a cross have been thought to indicate whether or not the parent-forms ought
to be ranked as species or varieties; but after carefully studying the
evidence, I have come to the conclusion that no general rules of this kind
can be trusted. The ordinary result of a cross is the production of a
blended or intermediate form; but in certain cases some of the offspring
take closely after one parent-form, and some after the other. This is
especially apt to occur when the parents differ in characters which first
appeared as sudden variations or monstrosities. (15. 'The Variation of
Animals,' etc., vol. ii. p. 92.) I refer to this point, because Dr. Rohlfs
informs me that he has frequently seen in Africa the offspring of negroes
crossed with members of other races, either completely black or completely
white, or rarely piebald. On the other hand, it is notorious that in
America mulattoes commonly present an intermediate appearance.
We have now seen that a naturalist might feel himself fully justified in
ranking the races of man as distinct species; for he has found that they
are distinguished by many differences in structure and constitution, some
being of importance. These differences have, also, remained nearly
constant for very long periods of time. Our naturalist will have been in
some degree influenced by the enormous range of man, which is a great
anomaly in the class of mammals, if mankind be viewed as a single species.
He will have been struck with the distribution of the several so-called
races, which accords with that of other undoubtedly distinct species of
mammals. Finally, he might urge that the mutual fertility of all the races
has not as yet been fully proved, and even if proved would not be an
absolute proof of their specific identity.
On the other side of the question, if our supposed naturalist were to
enquire whether the forms of man keep distinct like ordinary species, when
mingled together in large numbers in the same country, he would immediately
discover that this was by no means the case. In Brazil he would behold an
immense mongrel population of Negroes and Portuguese; in Chiloe, and other
parts of South America, he would behold the whole population consisting of
Indians and Spaniards blended in various degrees. (16. M. de Quatrefages
has given ('Anthropological Review,' Jan. 1869, p. 22), an interesting
account of the success and energy of the Paulistas in Brazil, who are a
much crossed race of Portuguese and Indians, with a mixture of the blood of
other races.) In many parts of the same continent he would meet with the
most complex crosses between Negroes, Indians, and Europeans; and judging
from the vegetable kingdom, such triple crosses afford the severest test of
the mutual fertility of the parent forms. In one island of the Pacific he
would find a small population of mingled Polynesian and English blood; and
in the Fiji Archipelago a population of Polynesian and Negritos crossed in
all degrees. Many analogous cases could be added; for instance, in Africa.
Hence the races of man are not sufficiently distinct to inhabit the same
country without fusion; and the absence of fusion affords the usual and
best test of specific distinctness.
Our naturalist would likewise be much disturbed as soon as he perceived
that the distinctive characters of all the races were highly variable.
This fact strikes every one on first beholding the negro slaves in Brazil,
who have been imported from all parts of Africa. The same remark holds
good with the Polynesians, and with many other races. It may be doubted
whether any character can be named which is distinctive of a race and is
constant. Savages, even within the limits of the same tribe, are not
nearly so uniform in character, as has been often asserted. Hottentot
women offer certain peculiarities, more strongly marked than those
occurring in any other race, but these are known not to be of constant
occurrence. In the several American tribes, colour and hairiness differ
considerably; as does colour to a certain degree, and the shape of the
features greatly, in the Negroes of Africa. The shape of the skull varies
much in some races (17. For instance, with the aborigines of America and
Australia, Prof. Huxley says ('Transact. Internat. Congress of Prehist.
Arch.' 1868, p. 105), that the skulls of many South Germans and Swiss are
"as short and as broad as those of the Tartars," etc.); and so it is with
every other character. Now all naturalists have learnt by dearly bought
experience, how rash it is to attempt to define species by the aid of
inconstant characters.
But the most weighty of all the arguments against treating the races of man
as distinct species, is that they graduate into each other, independently
in many cases, as far as we can judge, of their having intercrossed. Man
has been studied more carefully than any other animal, and yet there is the
greatest possible diversity amongst capable judges whether he should be
classed as a single species or race, or as two (Virey), as three
(Jacquinot), as four (Kant), five (Blumenbach), six (Buffon), seven
(Hunter), eight (Agassiz), eleven (Pickering), fifteen (Bory St. Vincent),
sixteen (Desmoulins), twenty-two (Morton), sixty (Crawfurd), or as sixty-
three, according to Burke. (18. See a good discussion on this subject in
Waitz, 'Introduction to Anthropology,' Eng. translat., 1863, pp. 198-208,
227. I have taken some of the above statements from H. Tuttle's 'Origin
and Antiquity of Physical Man,' Boston, 1866, p. 35.) This diversity of
judgment does not prove that the races ought not to be ranked as species,
but it shews that they graduate into each other, and that it is hardly
possible to discover clear distinctive characters between them.
Every naturalist who has had the misfortune to undertake the description of
a group of highly varying organisms, has encountered cases (I speak after
experience) precisely like that of man; and if of a cautious disposition,
he will end by uniting all the forms which graduate into each other, under
a single species; for he will say to himself that he has no right to give
names to objects which he cannot define. Cases of this kind occur in the
Order which includes man, namely in certain genera of monkeys; whilst in
other genera, as in Cercopithecus, most of the species can be determined
with certainty. In the American genus Cebus, the various forms are ranked
by some naturalists as species, by others as mere geographical races. Now
if numerous specimens of Cebus were collected from all parts of South
America, and those forms which at present appear to be specifically
distinct, were found to graduate into each other by close steps, they would
usually be ranked as mere varieties or races; and this course has been
followed by most naturalists with respect to the races of man.
Nevertheless, it must be confessed that there are forms, at least in the
vegetable kingdom (19. Prof. Nageli has carefully described several
striking cases in his 'Botanische Mittheilungen,' B. ii. 1866, ss. 294-369.
Prof. Asa Gray has made analogous remarks on some intermediate forms in the
Compositae of N. America.), which we cannot avoid naming as species, but
which are connected together by numberless gradations, independently of
intercrossing.
Some naturalists have lately employed the term "sub-species" to designate
forms which possess many of the characteristics of true species, but which
hardly deserve so high a rank. Now if we reflect on the weighty arguments
above given, for raising the races of man to the dignity of species, and
the insuperable difficulties on the other side in defining them, it seems
that the term "sub-species" might here be used with propriety. But from
long habit the term "race" will perhaps always be employed. The choice of
terms is only so far important in that it is desirable to use, as far as
possible, the same terms for the same degrees of difference. Unfortunately
this can rarely be done: for the larger genera generally include closely-
allied forms, which can be distinguished only with much difficulty, whilst
the smaller genera within the same family include forms that are perfectly
distinct; yet all must be ranked equally as species. So again, species
within the same large genus by no means resemble each other to the same
degree: on the contrary, some of them can generally be arranged in little
groups round other species, like satellites round planets. (20. 'Origin
of Species,' 5th edit. p. 68.)
The question whether mankind consists of one or several species has of late
years been much discussed by anthropologists, who are divided into the two
schools of monogenists and polygenists. Those who do not admit the
principle of evolution, must look at species as separate creations, or in
some manner as distinct entities; and they must decide what forms of man
they will consider as species by the analogy of the method commonly pursued
in ranking other organic beings as species. But it is a hopeless endeavour
to decide this point, until some definition of the term "species" is
generally accepted; and the definition must not include an indeterminate
element such as an act of creation. We might as well attempt without any
definition to decide whether a certain number of houses should be called a
village, town, or city. We have a practical illustration of the difficulty
in the never-ending doubts whether many closely-allied mammals, birds,
insects, and plants, which represent each other respectively in North
America and Europe, should be ranked as species or geographical races; and
the like holds true of the productions of many islands situated at some
little distance from the nearest continent.
Those naturalists, on the other hand, who admit the principle of evolution,
and this is now admitted by the majority of rising men, will feel no doubt
that all the races of man are descended from a single primitive stock;
whether or not they may think fit to designate the races as distinct
species, for the sake of expressing their amount of difference. (21. See
Prof. Huxley to this effect in the 'Fortnightly Review,' 1865, p. 275.)
With our domestic animals the question whether the various races have
arisen from one or more species is somewhat different. Although it may be
admitted that all the races, as well as all the natural species within the
same genus, have sprung from the same primitive stock, yet it is a fit
subject for discussion, whether all the domestic races of the dog, for
instance, have acquired their present amount of difference since some one
species was first domesticated by man; or whether they owe some of their
characters to inheritance from distinct species, which had already been
differentiated in a state of nature. With man no such question can arise,
for he cannot be said to have been domesticated at any particular period.
During an early stage in the divergence of the races of man from a common
stock, the differences between the races and their number must have been
small; consequently as far as their distinguishing characters are
concerned, they then had less claim to rank as distinct species than the
existing so-called races. Nevertheless, so arbitrary is the term of
species, that such early races would perhaps have been ranked by some
naturalists as distinct species, if their differences, although extremely
slight, had been more constant than they are at present, and had not
graduated into each other.
It is however possible, though far from probable, that the early
progenitors of man might formerly have diverged much in character, until
they became more unlike each other than any now existing races; but that
subsequently, as suggested by Vogt (22. 'Lectures on Man,' Eng. translat.,
1864, p. 468.), they converged in character. When man selects the
offspring of two distinct species for the same object, he sometimes induces
a considerable amount of convergence, as far as general appearance is
concerned. This is the case, as shewn by von Nathusius (23. 'Die Rassen
des Schweines,' 1860, s. 46. 'Vorstudien fur Geschichte,' etc.,
Schweinesschadel, 1864, s. 104. With respect to cattle, see M. de
Quatrefages, 'Unite de l'Espece Humaine,' 1861, p. 119.), with the improved
breeds of the pig, which are descended from two distinct species; and in a
less marked manner with the improved breeds of cattle. A great anatomist,
Gratiolet, maintains that the anthropomorphous apes do not form a natural
sub-group; but that the orang is a highly developed gibbon or
semnopithecus, the chimpanzee a highly developed macacus, and the gorilla a
highly developed mandrill. If this conclusion, which rests almost
exclusively on brain-characters, be admitted, we should have a case of
convergence at least in external characters, for the anthropomorphous apes
are certainly more like each other in many points, than they are to other
apes. All analogical resemblances, as of a whale to a fish, may indeed be
said to be cases of convergence; but this term has never been applied to
superficial and adaptive resemblances. It would, however, be extremely
rash to attribute to convergence close similarity of character in many
points of structure amongst the modified descendants of widely distinct
beings. The form of a crystal is determined solely by the molecular
forces, and it is not surprising that dissimilar substances should
sometimes assume the same form; but with organic beings we should bear in
mind that the form of each depends on an infinity of complex relations,
namely on variations, due to causes far too intricate to be followed,--on
the nature of the variations preserved, these depending on the physical
conditions, and still more on the surrounding organisms which compete with
each,--and lastly, on inheritance (in itself a fluctuating element) from
innumerable progenitors, all of which have had their forms determined
through equally complex relations. It appears incredible that the modified
descendants of two organisms, if these differed from each other in a marked
manner, should ever afterwards converge so closely as to lead to a near
approach to identity throughout their whole organisation. In the case of
the convergent races of pigs above referred to, evidence of their descent
from two primitive stocks is, according to von Nathusius, still plainly
retained, in certain bones of their skulls. If the races of man had
descended, as is supposed by some naturalists, from two or more species,
which differed from each other as much, or nearly as much, as does the
orang from the gorilla, it can hardly be doubted that marked differences in
the structure of certain bones would still be discoverable in man as he now
exists.
Although the existing races of man differ in many respects, as in colour,
hair, shape of skull, proportions of the body, etc., yet if their whole
structure be taken into consideration they are found to resemble each other
closely in a multitude of points. Many of these are of so unimportant or
of so singular a nature, that it is extremely improbable that they should
have been independently acquired by aboriginally distinct species or races.
The same remark holds good with equal or greater force with respect to the
numerous points of mental similarity between the most distinct races of
man. The American aborigines, Negroes and Europeans are as different from
each other in mind as any three races that can be named; yet I was
incessantly struck, whilst living with the Feugians on board the "Beagle,"
with the many little traits of character, shewing how similar their minds
were to ours; and so it was with a full-blooded negro with whom I happened
once to be intimate.
He who will read Mr. Tylor's and Sir J. Lubbock's interesting works (24.
Tylor's 'Early History of Mankind,' 1865: with respect to gesture-
language, see p. 54. Lubbock's 'Prehistoric Times,' 2nd edit. 1869.) can
hardly fail to be deeply impressed with the close similarity between the
men of all races in tastes, dispositions and habits. This is shewn by the
pleasure which they all take in dancing, rude music, acting, painting,
tattooing, and otherwise decorating themselves; in their mutual
comprehension of gesture-language, by the same expression in their
features, and by the same inarticulate cries, when excited by the same
emotions. This similarity, or rather identity, is striking, when
contrasted with the different expressions and cries made by distinct
species of monkeys. There is good evidence that the art of shooting with
bows and arrows has not been handed down from any common progenitor of
mankind, yet as Westropp and Nilsson have remarked (25. 'On Analogous
Forms of Implements,' in 'Memoirs of Anthropological Society' by H.M.
Westropp. 'The Primitive Inhabitants of Scandinavia,' Eng. translat.,
edited by Sir J. Lubbock, 1868, p. 104.), the stone arrow-heads, brought
from the most distant parts of the world, and manufactured at the most
remote periods, are almost identical; and this fact can only be accounted
for by the various races having similar inventive or mental powers. The
same observation has been made by archaeologists (26. Westropp 'On
Cromlechs,' etc., 'Journal of Ethnological Soc.' as given in 'Scientific
Opinion,' June 2nd, 1869, p. 3.) with respect to certain widely-prevalent
ornaments, such as zig-zags, etc.; and with respect to various simple
beliefs and customs, such as the burying of the dead under megalithic
structures. I remember observing in South America (27. 'Journal of
Researches: Voyage of the "Beagle,"' p. 46.), that there, as in so many
other parts of the world, men have generally chosen the summits of lofty
hills, to throw up piles of stones, either as a record of some remarkable
event, or for burying their dead.
Now when naturalists observe a close agreement in numerous small details of
habits, tastes, and dispositions between two or more domestic races, or
between nearly-allied natural forms, they use this fact as an argument that
they are descended from a common progenitor who was thus endowed; and
consequently that all should be classed under the same species. The same
argument may be applied with much force to the races of man.
As it is improbable that the numerous and unimportant points of resemblance
between the several races of man in bodily structure and mental faculties
(I do not here refer to similar customs) should all have been independently
acquired, they must have been inherited from progenitors who had these same
characters. We thus gain some insight into the early state of man, before
he had spread step by step over the face of the earth. The spreading of
man to regions widely separated by the sea, no doubt, preceded any great
amount of divergence of character in the several races; for otherwise we
should sometimes meet with the same race in distinct continents; and this
is never the case. Sir J. Lubbock, after comparing the arts now practised
by savages in all parts of the world, specifies those which man could not
have known, when he first wandered from his original birthplace; for if
once learnt they would never have been forgotten. (28. 'Prehistoric
Times,' 1869, p. 574.) He thus shews that "the spear, which is but a
development of the knife-point, and the club, which is but a long hammer,
are the only things left." He admits, however, that the art of making fire
probably had been already discovered, for it is common to all the races now
existing, and was known to the ancient cave-inhabitants of Europe. Perhaps
the art of making rude canoes or rafts was likewise known; but as man
existed at a remote epoch, when the land in many places stood at a very
different level to what it does now, he would have been able, without the
aid of canoes, to have spread widely. Sir J. Lubbock further remarks how
improbable it is that our earliest ancestors could have "counted as high as
ten, considering that so many races now in existence cannot get beyond
four." Nevertheless, at this early period, the intellectual and social
faculties of man could hardly have been inferior in any extreme degree to
those possessed at present by the lowest savages; otherwise primeval man
could not have been so eminently successful in the struggle for life, as
proved by his early and wide diffusion.
From the fundamental differences between certain languages, some
philologists have inferred that when man first became widely diffused, he
was not a speaking animal; but it may be suspected that languages, far less
perfect than any now spoken, aided by gestures, might have been used, and
yet have left no traces on subsequent and more highly-developed tongues.
Without the use of some language, however imperfect, it appears doubtful
whether man's intellect could have risen to the standard implied by his
dominant position at an early period.
Whether primeval man, when he possessed but few arts, and those of the
rudest kind, and when his power of language was extremely imperfect, would
have deserved to be called man, must depend on the definition which we
employ. In a series of forms graduating insensibly from some ape-like
creature to man as he now exists, it would be impossible to fix on any
definite point where the term "man" ought to be used. But this is a matter
of very little importance. So again, it is almost a matter of indifference
whether the so-called races of man are thus designated, or are ranked as
species or sub-species; but the latter term appears the more appropriate.
Finally, we may conclude that when the principle of evolution is generally
accepted, as it surely will be before long, the dispute between the
monogenists and the polygenists will die a silent and unobserved death.
One other question ought not to be passed over without notice, namely,
whether, as is sometimes assumed, each sub-species or race of man has
sprung from a single pair of progenitors. With our domestic animals a new
race can readily be formed by carefully matching the varying offspring from
a single pair, or even from a single individual possessing some new
character; but most of our races have been formed, not intentionally from a
selected pair, but unconsciously by the preservation of many individuals
which have varied, however slightly, in some useful or desired manner. If
in one country stronger and heavier horses, and in another country lighter
and fleeter ones, were habitually preferred, we may feel sure that two
distinct sub-breeds would be produced in the course of time, without any
one pair having been separated and bred from, in either country. Many
races have been thus formed, and their manner of formation is closely
analogous to that of natural species. We know, also, that the horses taken
to the Falkland Islands have, during successive generations, become smaller
and weaker, whilst those which have run wild on the Pampas have acquired
larger and coarser heads; and such changes are manifestly due, not to any
one pair, but to all the individuals having been subjected to the same
conditions, aided, perhaps, by the principle of reversion. The new sub-
breeds in such cases are not descended from any single pair, but from many
individuals which have varied in different degrees, but in the same general
manner; and we may conclude that the races of man have been similarly
produced, the modifications being either the direct result of exposure to
different conditions, or the indirect result of some form of selection.
But to this latter subject we shall presently return.
ON THE EXTINCTION OF THE RACES OF MAN.
The partial or complete extinction of many races and sub-races of man is
historically known. Humboldt saw in South America a parrot which was the
sole living creature that could speak a word of the language of a lost
tribe. Ancient monuments and stone implements found in all parts of the
world, about which no tradition has been preserved by the present
inhabitants, indicate much extinction. Some small and broken tribes,
remnants of former races, still survive in isolated and generally
mountainous districts. In Europe the ancient races were all, according to
Shaaffhausen (29. Translation in 'Anthropological Review,' Oct. 1868, p.
431.), "lower in the scale than the rudest living savages"; they must
therefore have differed, to a certain extent, from any existing race. The
remains described by Professor Broca from Les Eyzies, though they
unfortunately appear to have belonged to a single family, indicate a race
with a most singular combination of low or simious, and of high
characteristics. This race is "entirely different from any other, ancient
or modern, that we have heard of." (30. 'Transactions, International
Congress of Prehistoric Archaeology' 1868, pp. 172-175. See also Broca
(tr.) in 'Anthropological Review,' Oct. 1868, p. 410.) It differed,
therefore, from the quaternary race of the caverns of Belgium.
Man can long resist conditions which appear extremely unfavourable for his
existence. (31. Dr. Gerland, 'Ueber das Aussterben der Naturvolker,'
1868, s. 82.) He has long lived in the extreme regions of the North, with
no wood for his canoes or implements, and with only blubber as fuel, and
melted snow as drink. In the southern extremity of America the Fuegians
survive without the protection of clothes, or of any building worthy to be
called a hovel. In South Africa the aborigines wander over arid plains,
where dangerous beasts abound. Man can withstand the deadly influence of
the Terai at the foot of the Himalaya, and the pestilential shores of
tropical Africa.
Extinction follows chiefly from the competition of tribe with tribe, and
race with race. Various checks are always in action, serving to keep down
the numbers of each savage tribe,--such as periodical famines, nomadic
habits and the consequent deaths of infants, prolonged suckling, wars,
accidents, sickness, licentiousness, the stealing of women, infanticide,
and especially lessened fertility. If any one of these checks increases in
power, even slightly, the tribe thus affected tends to decrease; and when
of two adjoining tribes one becomes less numerous and less powerful than
the other, the contest is soon settled by war, slaughter, cannibalism,
slavery, and absorption. Even when a weaker tribe is not thus abruptly
swept away, if it once begins to decrease, it generally goes on decreasing
until it becomes extinct. (32. Gerland (ibid. s. 12) gives facts in
support of this statement.)
When civilised nations come into contact with barbarians the struggle is
short, except where a deadly climate gives its aid to the native race. Of
the causes which lead to the victory of civilised nations, some are plain
and simple, others complex and obscure. We can see that the cultivation of
the land will be fatal in many ways to savages, for they cannot, or will
not, change their habits. New diseases and vices have in some cases proved
highly destructive; and it appears that a new disease often causes much
death, until those who are most susceptible to its destructive influence
are gradually weeded out (33. See remarks to this effect in Sir H.
Holland's 'Medical Notes and Reflections,' 1839, p. 390.); and so it may be
with the evil effects from spirituous liquors, as well as with the
unconquerably strong taste for them shewn by so many savages. It further
appears, mysterious as is the fact, that the first meeting of distinct and
separated people generates disease. (34. I have collected ('Journal of
Researches: Voyage of the "Beagle,"' p. 435) a good many cases bearing on
this subject; see also Gerland, ibid. s. 8. Poeppig speaks of the "breath
of civilisation as poisonous to savages.") Mr. Sproat, who in Vancouver
Island closely attended to the subject of extinction, believed that changed
habits of life, consequent on the advent of Europeans, induces much ill
health. He lays, also, great stress on the apparently trifling cause that
the natives become "bewildered and dull by the new life around them; they
lose the motives for exertion, and get no new ones in their place." (35.
Sproat, 'Scenes and Studies of Savage Life,' 1868, p. 284.)
The grade of their civilisation seems to be a most important element in the
success of competing nations. A few centuries ago Europe feared the
inroads of Eastern barbarians; now any such fear would be ridiculous. It
is a more curious fact, as Mr. Bagehot has remarked, that savages did not
formerly waste away before the classical nations, as they now do before
modern civilised nations; had they done so, the old moralists would have
mused over the event; but there is no lament in any writer of that period
over the perishing barbarians. (36. Bagehot, 'Physics and Politics,'
'Fortnightly Review,' April 1, 1868, p. 455.) The most potent of all the
causes of extinction, appears in many cases to be lessened fertility and
ill-health, especially amongst the children, arising from changed
conditions of life, notwithstanding that the new conditions may not be
injurious in themselves. I am much indebted to Mr. H.H. Howorth for having
called my attention to this subject, and for having given me information
respecting it. I have collected the following cases.
When Tasmania was first colonised the natives were roughly estimated by
some at 7000 and by others at 20,000. Their number was soon greatly
reduced, chiefly by fighting with the English and with each other. After
the famous hunt by all the colonists, when the remaining natives delivered
themselves up to the government, they consisted only of 120 individuals
(37. All the statements here given are taken from 'The Last of the
Tasmanians,' by J. Bonwick, 1870.), who were in 1832 transported to
Flinders Island. This island, situated between Tasmania and Australia, is
forty miles long, and from twelve to eighteen miles broad: it seems
healthy, and the natives were well treated. Nevertheless, they suffered
greatly in health. In 1834 they consisted (Bonwick, p. 250) of forty-seven
adult males, forty-eight adult females, and sixteen children, or in all of
111 souls. In 1835 only one hundred were left. As they continued rapidly
to decrease, and as they themselves thought that they should not perish so
quickly elsewhere, they were removed in 1847 to Oyster Cove in the southern
part of Tasmania. They then consisted (Dec. 20th, 1847) of fourteen men,
twenty-two women and ten children. (38. This is the statement of the
Governor of Tasmania, Sir W. Denison, 'Varieties of Vice-Regal Life,' 1870,
vol. i. p. 67.) But the change of site did no good. Disease and death
still pursued them, and in 1864 one man (who died in 1869), and three
elderly women alone survived. The infertility of the women is even a more
remarkable fact than the liability of all to ill-health and death. At the
time when only nine women were left at Oyster Cove, they told Mr. Bonwick
(p. 386), that only two had ever borne children: and these two had
together produced only three children!
With respect to the cause of this extraordinary state of things, Dr. Story
remarks that death followed the attempts to civilise the natives. "If left
to themselves to roam as they were wont and undisturbed, they would have
reared more children, and there would have been less mortality." Another
careful observer of the natives, Mr. Davis, remarks, "The births have been
few and the deaths numerous. This may have been in a great measure owing
to their change of living and food; but more so to their banishment from
the mainland of Van Diemen's Land, and consequent depression of spirits"
(Bonwick, pp. 388, 390).
Similar facts have been observed in two widely different parts of
Australia. The celebrated explorer, Mr. Gregory, told Mr. Bonwick, that in
Queensland "the want of reproduction was being already felt with the
blacks, even in the most recently settled parts, and that decay would set
in." Of thirteen aborigines from Shark's Bay who visited Murchison River,
twelve died of consumption within three months. (39. For these cases, see
Bonwick's 'Daily Life of the Tasmanians,' 1870, p. 90: and the 'Last of
the Tasmanians,' 1870, p. 386.)
The decrease of the Maories of New Zealand has been carefully investigated
by Mr. Fenton, in an admirable Report, from which all the following
statements, with one exception, are taken. (40. 'Observations on the
Aboriginal Inhabitants of New Zealand,' published by the Government, 1859.)
The decrease in number since 1830 is admitted by every one, including the
natives themselves, and is still steadily progressing. Although it has
hitherto been found impossible to take an actual census of the natives,
their numbers were carefully estimated by residents in many districts. The
result seems trustworthy, and shows that during the fourteen years,
previous to 1858, the decrease was 19.42 per cent. Some of the tribes,
thus carefully examined, lived above a hundred miles apart, some on the
coast, some inland; and their means of subsistence and habits differed to a
certain extent (p. 28). The total number in 1858 was believed to be
53,700, and in 1872, after a second interval of fourteen years, another
census was taken, and the number is given as only 36,359, shewing a
decrease of 32.29 per cent! (41. 'New Zealand,' by Alex. Kennedy, 1873,
p. 47.) Mr. Fenton, after shewing in detail the insufficiency of the
various causes, usually assigned in explanation of this extraordinary
decrease, such as new diseases, the profligacy of the women, drunkenness,
wars, etc., concludes on weighty grounds that it depends chiefly on the
unproductiveness of the women, and on the extraordinary mortality of the
young children (pp. 31, 34). In proof of this he shews (p. 33) that in
1844 there was one non-adult for every 2.57 adults; whereas in 1858 there
was only one non-adult for every 3.27 adults. The mortality of the adults
is also great. He adduces as a further cause of the decrease the
inequality of the sexes; for fewer females are born than males. To this
latter point, depending perhaps on a widely distinct cause, I shall return
in a future chapter. Mr. Fenton contrasts with astonishment the decrease
in New Zealand with the increase in Ireland; countries not very dissimilar
in climate, and where the inhabitants now follow nearly similar habits.
The Maories themselves (p. 35) "attribute their decadence, in some measure,
to the introduction of new food and clothing, and the attendant change of
habits"; and it will be seen, when we consider the influence of changed
conditions on fertility, that they are probably right. The diminution
began between the years 1830 and 1840; and Mr. Fenton shews (p. 40) that
about 1830, the art of manufacturing putrid corn (maize), by long steeping
in water, was discovered and largely practised; and this proves that a
change of habits was beginning amongst the natives, even when New Zealand
was only thinly inhabited by Europeans. When I visited the Bay of Islands
in 1835, the dress and food of the inhabitants had already been much
modified: they raised potatoes, maize, and other agricultural produce, and
exchanged them for English manufactured goods and tobacco.
It is evident from many statements in the life of Bishop Patteson (42.
'Life of J.C. Patteson,' by C.M. Younge, 1874; see more especially vol. i.
p. 530.), that the Melanesians of the New Hebrides and neighbouring
archipelagoes, suffered to an extraordinary degree in health, and perished
in large numbers, when they were removed to New Zealand, Norfolk Island,
and other salubrious places, in order to be educated as missionaries.
The decrease of the native population of the Sandwich Islands is as
notorious as that of New Zealand. It has been roughly estimated by those
best capable of judging, that when Cook discovered the Islands in 1779, the
population amounted to about 300,000. According to a loose census in 1823,
the numbers then were 142,050. In 1832, and at several subsequent periods,
an accurate census was officially taken, but I have been able to obtain
only the following returns:
Native Population Annual rate of decrease
per cent., assuming it to
(Except during 1832 and have been uniform between
1836, when the few the successive censuses;
foreigners in the islands these censuses being taken
Year were included.) at irregular intervals.
1832 130,313
4.46
1836 108,579
2.47
1853 71,019
0.81
1860 67,084
2.18
1866 58,765
2.17
1872 51,531
We here see that in the interval of forty years, between 1832 and 1872, the
population has decreased no less than sixty-eight per cent.! This has been
attributed by most writers to the profligacy of the women, to former bloody
wars, and to the severe labour imposed on conquered tribes and to newly
introduced diseases, which have been on several occasions extremely
destructive. No doubt these and other such causes have been highly
efficient, and may account for the extraordinary rate of decrease between
the years 1832 and 1836; but the most potent of all the causes seems to be
lessened fertility. According to Dr. Ruschenberger of the U.S. Navy, who
visited these islands between 1835 and 1837, in one district of Hawaii,
only twenty-five men out of 1134, and in another district only ten out of
637, had a family with as many as three children. Of eighty married women,
only thirty-nine had ever borne children; and "the official report gives an
average of half a child to each married couple in the whole island." This
is almost exactly the same average as with the Tasmanians at Oyster Cove.
Jarves, who published his History in 1843, says that "families who have
three children are freed from all taxes; those having more, are rewarded by
gifts of land and other encouragements." This unparalleled enactment by
the government well shews how infertile the race had become. The Rev. A.
Bishop stated in the Hawaiian 'Spectator' in 1839, that a large proportion
of the children die at early ages, and Bishop Staley informs me that this
is still the case, just as in New Zealand. This has been attributed to the
neglect of the children by the women, but it is probably in large part due
to innate weakness of constitution in the children, in relation to the
lessened fertility of their parents. There is, moreover, a further
resemblance to the case of New Zealand, in the fact that there is a large
excess of male over female births: the census of 1872 gives 31,650 males
to 25,247 females of all ages, that is 125.36 males for every 100 females;
whereas in all civilised countries the females exceed the males. No doubt
the profligacy of the women may in part account for their small fertility;
but their changed habits of life is a much more probable cause, and which
will at the same time account for the increased mortality, especially of
the children. The islands were visited by Cook in 1779, Vancouver in 1794,
and often subsequently by whalers. In 1819 missionaries arrived, and found
that idolatry had been already abolished, and other changes effected by the
king. After this period there was a rapid change in almost all the habits
of life of the natives, and they soon became "the most civilised of the
Pacific Islanders." One of my informants, Mr. Coan, who was born on the
islands, remarks that the natives have undergone a greater change in their
habits of life in the course of fifty years than Englishmen during a
thousand years. From information received from Bishop Staley, it does not
appear that the poorer classes have ever much changed their diet, although
many new kinds of fruit have been introduced, and the sugar-cane is in
universal use. Owing, however, to their passion for imitating Europeans,
they altered their manner of dressing at an early period, and the use of
alcoholic drinks became very general. Although these changes appear
inconsiderable, I can well believe, from what is known with respect to
animals, that they might suffice to lessen the fertility of the natives.
(43. The foregoing statements are taken chiefly from the following works:
Jarves' 'History of the Hawaiian Islands,' 1843, pp. 400-407. Cheever,
'Life in the Sandwich Islands,' 1851, p. 277. Ruschenberger is quoted by
Bonwick, 'Last of the Tasmanians,' 1870, p. 378. Bishop is quoted by Sir
E. Belcher, 'Voyage Round the World,' 1843, vol. i. p. 272. I owe the
census of the several years to the kindness of Mr. Coan, at the request of
Dr. Youmans of New York; and in most cases I have compared the Youmans
figures with those given in several of the above-named works. I have
omitted the census for 1850, as I have seen two widely different numbers
given.)
Lastly, Mr. Macnamara states (44. 'The Indian Medical Gazette,' Nov. 1,
1871, p. 240.) that the low and degraded inhabitants of the Andaman
Islands, on the eastern side of the Gulf of Bengal, are "eminently
susceptible to any change of climate: in fact, take them away from their
island homes, and they are almost certain to die, and that independently of
diet or extraneous influences." He further states that the inhabitants of
the Valley of Nepal, which is extremely hot in summer, and also the various
hill-tribes of India, suffer from dysentery and fever when on the plains;
and they die if they attempt to pass the whole year there.
We thus see that many of the wilder races of man are apt to suffer much in
health when subjected to changed conditions or habits of life, and not
exclusively from being transported to a new climate. Mere alterations in
habits, which do not appear injurious in themselves, seem to have this same
effect; and in several cases the children are particularly liable to
suffer. It has often been said, as Mr. Macnamara remarks, that man can
resist with impunity the greatest diversities of climate and other changes;
but this is true only of the civilised races. Man in his wild condition
seems to be in this respect almost as susceptible as his nearest allies,
the anthropoid apes, which have never yet survived long, when removed from
their native country.
Lessened fertility from changed conditions, as in the case of the
Tasmanians, Maories, Sandwich Islanders, and apparently the Australians, is
still more interesting than their liability to ill-health and death; for
even a slight degree of infertility, combined with those other causes which
tend to check the increase of every population, would sooner or later lead
to extinction. The diminution of fertility may be explained in some cases
by the profligacy of the women (as until lately with the Tahitians), but
Mr. Fenton has shewn that this explanation by no means suffices with the
New Zealanders, nor does it with the Tasmanians.
In the paper above quoted, Mr. Macnamara gives reasons for believing that
the inhabitants of districts subject to malaria are apt to be sterile; but
this cannot apply in several of the above cases. Some writers have
suggested that the aborigines of islands have suffered in fertility and
health from long continued inter-breeding; but in the above cases
infertility has coincided too closely with the arrival of Europeans for us
to admit this explanation. Nor have we at present any reason to believe
that man is highly sensitive to the evil effects of inter-breeding,
especially in areas so large as New Zealand, and the Sandwich archipelago
with its diversified stations. On the contrary, it is known that the
present inhabitants of Norfolk Island are nearly all cousins or near
relations, as are the Todas in India, and the inhabitants of some of the
Western Islands of Scotland; and yet they seem not to have suffered in
fertility. (45. On the close relationship of the Norfolk Islanders, Sir
W. Denison, 'Varieties of Vice-Regal Life,' vol. i. 1870, p. 410. For the
Todas, see Col. Marshall's work 1873, p. 110. For the Western Islands of
Scotland, Dr. Mitchell, 'Edinburgh Medical Journal,' March to June, 1865.)
A much more probable view is suggested by the analogy of the lower animals.
The reproductive system can be shewn to be susceptible to an extraordinary
degree (though why we know not) to changed conditions of life; and this
susceptibility leads both to beneficial and to evil results. A large
collection of facts on this subject is given in chap. xviii. of vol. ii. of
my 'Variation of Animals and Plants under Domestication,' I can here give
only the briefest abstract; and every one interested in the subject may
consult the above work. Very slight changes increase the health, vigour,
and fertility of most or all organic beings, whilst other changes are known
to render a large number of animals sterile. One of the most familiar
cases, is that of tamed elephants not breeding in India; though they often
breed in Ava, where the females are allowed to roam about the forests to
some extent, and are thus placed under more natural conditions. The case
of various American monkeys, both sexes of which have been kept for many
years together in their own countries, and yet have very rarely or never
bred, is a more apposite instance, because of their relationship to man.
It is remarkable how slight a change in the conditions often induces
sterility in a wild animal when captured; and this is the more strange as
all our domesticated animals have become more fertile than they were in a
state of nature; and some of them can resist the most unnatural conditions
with undiminished fertility. (46. For the evidence on this head, see
'Variation of Animals,' etc., vol. ii. p. 111.) Certain groups of animals
are much more liable than others to be affected by captivity; and generally
all the species of the same group are affected in the same manner. But
sometimes a single species in a group is rendered sterile, whilst the
others are not so; on the other hand, a single species may retain its
fertility whilst most of the others fail to breed. The males and females
of some species when confined, or when allowed to live almost, but not
quite free, in their native country, never unite; others thus circumstanced
frequently unite but never produce offspring; others again produce some
offspring, but fewer than in a state of nature; and as bearing on the above
cases of man, it is important to remark that the young are apt to be weak
and sickly, or malformed, and to perish at an early age.
Seeing how general is this law of the susceptibility of the reproductive
system to changed conditions of life, and that it holds good with our
nearest allies, the Quadrumana, I can hardly doubt that it applies to man
in his primeval state. Hence if savages of any race are induced suddenly
to change their habits of life, they become more or less sterile, and their
young offspring suffer in health, in the same manner and from the same
cause, as do the elephant and hunting-leopard in India, many monkeys in
America, and a host of animals of all kinds, on removal from their natural
conditions.
We can see why it is that aborigines, who have long inhabited islands, and
who must have been long exposed to nearly uniform conditions, should be
specially affected by any change in their habits, as seems to be the case.
Civilised races can certainly resist changes of all kinds far better than
savages; and in this respect they resemble domesticated animals, for though
the latter sometimes suffer in health (for instance European dogs in
India), yet they are rarely rendered sterile, though a few such instances
have been recorded. (47. 'Variation of Animals,' etc., vol. ii. p. 16.)
The immunity of civilised races and domesticated animals is probably due to
their having been subjected to a greater extent, and therefore having grown
somewhat more accustomed, to diversified or varying conditions, than the
majority of wild animals; and to their having formerly immigrated or been
carried from country to country, and to different families or sub-races
having inter-crossed. It appears that a cross with civilised races at once
gives to an aboriginal race an immunity from the evil consequences of
changed conditions. Thus the crossed offspring from the Tahitians and
English, when settled in Pitcairn Island, increased so rapidly that the
island was soon overstocked; and in June 1856 they were removed to Norfolk
Island. They then consisted of 60 married persons and 134 children, making
a total of 194. Here they likewise increased so rapidly, that although
sixteen of them returned to Pitcairn Island in 1859, they numbered in
January 1868, 300 souls; the males and females being in exactly equal
numbers. What a contrast does this case present with that of the
Tasmanians; the Norfolk Islanders INCREASED in only twelve and a half years
from 194 to 300; whereas the Tasmanians DECREASED during fifteen years from
120 to 46, of which latter number only ten were children. (48. These
details are taken from 'The Mutineers of the "Bounty,"' by Lady Belcher,
1870; and from 'Pitcairn Island,' ordered to be printed by the House of
Commons, May 29, 1863. The following statements about the Sandwich
Islanders are from the 'Honolulu Gazette,' and from Mr. Coan.)
So again in the interval between the census of 1866 and 1872 the natives of
full blood in the Sandwich Islands decreased by 8081, whilst the half-
castes, who are believed to be healthier, increased by 847; but I do not
know whether the latter number includes the offspring from the half-castes,
or only the half-castes of the first generation.
The cases which I have here given all relate to aborigines, who have been
subjected to new conditions as the result of the immigration of civilised
men. But sterility and ill-health would probably follow, if savages were
compelled by any cause, such as the inroad of a conquering tribe, to desert
their homes and to change their habits. It is an interesting circumstance
that the chief check to wild animals becoming domesticated, which implies
the power of their breeding freely when first captured, and one chief check
to wild men, when brought into contact with civilisation, surviving to form
a civilised race, is the same, namely, sterility from changed conditions of
life.
Finally, although the gradual decrease and ultimate extinction of the races
of man is a highly complex problem, depending on many causes which differ
in different places and at different times; it is the same problem as that
presented by the extinction of one of the higher animals--of the fossil
horse, for instance, which disappeared from South America, soon afterwards
to be replaced, within the same districts, by countless troups of the
Spanish horse. The New Zealander seems conscious of this parallelism, for
he compares his future fate with that of the native rat now almost
exterminated by the European rat. Though the difficulty is great to our
imagination, and really great, if we wish to ascertain the precise causes
and their manner of action, it ought not to be so to our reason, as long as
we keep steadily in mind that the increase of each species and each race is
constantly checked in various ways; so that if any new check, even a slight
one, be superadded, the race will surely decrease in number; and decreasing
numbers will sooner or later lead to extinction; the end, in most cases,
being promptly determined by the inroads of conquering tribes.
ON THE FORMATION OF THE RACES OF MAN.
In some cases the crossing of distinct races has led to the formation of a
new race. The singular fact that the Europeans and Hindoos, who belong to
the same Aryan stock, and speak a language fundamentally the same, differ
widely in appearance, whilst Europeans differ but little from Jews, who
belong to the Semitic stock, and speak quite another language, has been
accounted for by Broca (49. 'On Anthropology,' translation,
'Anthropological Review,' Jan. 1868, p. 38.), through certain Aryan
branches having been largely crossed by indigenous tribes during their wide
diffusion. When two races in close contact cross, the first result is a
heterogeneous mixture: thus Mr. Hunter, in describing the Santali or hill-
tribes of India, says that hundreds of imperceptible gradations may be
traced "from the black, squat tribes of the mountains to the tall olive-
coloured Brahman, with his intellectual brow, calm eyes, and high but
narrow head"; so that it is necessary in courts of justice to ask the
witnesses whether they are Santalis or Hindoos. (50. 'The Annals of Rural
Bengal,' 1868, p. 134.) Whether a heterogeneous people, such as the
inhabitants of some of the Polynesian islands, formed by the crossing of
two distinct races, with few or no pure members left, would ever become
homogeneous, is not known from direct evidence. But as with our
domesticated animals, a cross-breed can certainly be fixed and made uniform
by careful selection (51. 'The Variation of Animals and Plants under
Domestication,' vol. ii. p. 95.) in the course of a few generations, we may
infer that the free intercrossing of a heterogeneous mixture during a long
descent would supply the place of selection, and overcome any tendency to
reversion; so that the crossed race would ultimately become homogeneous,
though it might not partake in an equal degree of the characters of the two
parent-races.
Of all the differences between the races of man, the colour of the skin is
the most conspicuous and one of the best marked. It was formerly thought
that differences of this kind could be accounted for by long exposure to
different climates; but Pallas first shewed that this is not tenable, and
he has since been followed by almost all anthropologists. (52. Pallas,
'Act. Acad. St. Petersburg,' 1780, part ii. p. 69. He was followed by
Rudolphi, in his 'Beytrage zur Anthropologie,' 1812. An excellent summary
of the evidence is given by Godron, 'De l'Espece,' 1859, vol. ii. p. 246,
etc.) This view has been rejected chiefly because the distribution of the
variously coloured races, most of whom must have long inhabited their
present homes, does not coincide with corresponding differences of climate.
Some little weight may be given to such cases as that of the Dutch
families, who, as we hear on excellent authority (53. Sir Andrew Smith, as
quoted by Knox, 'Races of Man,' 1850, p. 473.), have not undergone the
least change of colour after residing for three centuries in South Africa.
An argument on the same side may likewise be drawn from the uniform
appearance in various parts of the world of gipsies and Jews, though the
uniformity of the latter has been somewhat exaggerated. (54. See De
Quatrefages on this head, 'Revue des Cours Scientifiques,' Oct. 17, 1868,
p. 731.) A very damp or a very dry atmosphere has been supposed to be more
influential in modifying the colour of the skin than mere heat; but as
D'Orbigny in South America, and Livingstone in Africa, arrived at
diametrically opposite conclusions with respect to dampness and dryness,
any conclusion on this head must be considered as very doubtful. (55.
Livingstone's 'Travels and Researches in S. Africa,' 1857, pp. 338, 339.
D'Orbigny, as quoted by Godron, 'De l'Espece,' vol. ii. p. 266.)
Various facts, which I have given elsewhere, prove that the colour of the
skin and hair is sometimes correlated in a surprising manner with a
complete immunity from the action of certain vegetable poisons, and from
the attacks of certain parasites. Hence it occurred to me, that negroes
and other dark races might have acquired their dark tints by the darker
individuals escaping from the deadly influence of the miasma of their
native countries, during a long series of generations.
I afterwards found that this same idea had long ago occurred to Dr. Wells.
(56. See a paper read before the Royal Soc. in 1813, and published in his
Essays in 1818. I have given an account of Dr. Wells' views in the
Historical Sketch (p. xvi.) to my 'Origin of Species.' Various cases of
colour correlated with constitutional peculiarities are given in my
'Variation of Animals and Plants under Domestication,' vol. ii. pp. 227,
335.) It has long been known that negroes, and even mulattoes, are almost
completely exempt from the yellow-fever, so destructive in tropical
America. (57. See, for instance, Nott and Gliddon, 'Types of Mankind,' p.
68.) They likewise escape to a large extent the fatal intermittent fevers,
that prevail along at least 2600 miles of the shores of Africa, and which
annually cause one-fifth of the white settlers to die, and another fifth to
return home invalided. (58. Major Tulloch, in a paper read before the
Statistical Society, April 20, 1840, and given in the 'Athenaeum,' 1840, p.
353.) This immunity in the negro seems to be partly inherent, depending on
some unknown peculiarity of constitution, and partly the result of
acclimatisation. Pouchet (59. 'The Plurality of the Human Race'
(translat.), 1864, p. 60.) states that the negro regiments recruited near
the Soudan, and borrowed from the Viceroy of Egypt for the Mexican war,
escaped the yellow-fever almost equally with the negroes originally brought
from various parts of Africa and accustomed to the climate of the West
Indies. That acclimatisation plays a part, is shewn by the many cases in
which negroes have become somewhat liable to tropical fevers, after having
resided for some time in a colder climate. (60. Quatrefages, 'Unite de
l'Espece Humaine,' 1861, p. 205. Waitz, 'Introduction to Anthropology,'
translat., vol. i. 1863, p. 124. Livingstone gives analogous cases in his
'Travels.') The nature of the climate under which the white races have
long resided, likewise has some influence on them; for during the fearful
epidemic of yellow fever in Demerara during 1837, Dr. Blair found that the
death-rate of the immigrants was proportional to the latitude of the
country whence they had come. With the negro the immunity, as far as it is
the result of acclimatisation, implies exposure during a prodigious length
of time; for the aborigines of tropical America who have resided there from
time immemorial, are not exempt from yellow fever; and the Rev. H.B.
Tristram states, that there are districts in Northern Africa which the
native inhabitants are compelled annually to leave, though the negroes can
remain with safety.
That the immunity of the negro is in any degree correlated with the colour
of his skin is a mere conjecture: it may be correlated with some
difference in his blood, nervous system, or other tissues. Nevertheless,
from the facts above alluded to, and from some connection apparently
existing between complexion and a tendency to consumption, the conjecture
seemed to me not improbable. Consequently I endeavoured, with but little
success (61. In the spring of 1862 I obtained permission from the
Director-General of the Medical department of the Army, to transmit to the
surgeons of the various regiments on foreign service a blank table, with
the following appended remarks, but I have received no returns. "As
several well-marked cases have been recorded with our domestic animals of a
relation between the colour of the dermal appendages and the constitution;
and it being notorious that there is some limited degree of relation
between the colour of the races of man and the climate inhabited by them;
the following investigation seems worth consideration. Namely, whether
there is any relation in Europeans between the colour of their hair, and
their liability to the diseases of tropical countries. If the surgeons of
the several regiments, when stationed in unhealthy tropical districts,
would be so good as first to count, as a standard of comparison, how many
men, in the force whence the sick are drawn, have dark and light-coloured
hair, and hair of intermediate or doubtful tints; and if a similar account
were kept by the same medical gentlemen, of all the men who suffered from
malarious and yellow fevers, or from dysentery, it would soon be apparent,
after some thousand cases had been tabulated, whether there exists any
relation between the colour of the hair and constitutional liability to
tropical diseases. Perhaps no such relation would be discovered, but the
investigation is well worth making. In case any positive result were
obtained, it might be of some practical use in selecting men for any
particular service. Theoretically the result would be of high interest, as
indicating one means by which a race of men inhabiting from a remote period
an unhealthy tropical climate, might have become dark-coloured by the
better preservation of dark-haired or dark-complexioned individuals during
a long succession of generations."), to ascertain how far it holds good.
The late Dr. Daniell, who had long lived on the West Coast of Africa, told
me that he did not believe in any such relation. He was himself unusually
fair, and had withstood the climate in a wonderful manner. When he first
arrived as a boy on the coast, an old and experienced negro chief predicted
from his appearance that this would prove the case. Dr. Nicholson, of
Antigua, after having attended to this subject, writes to me that dark-
coloured Europeans escape the yellow fever more than those that are light-
coloured. Mr. J.M. Harris altogether denies that Europeans with dark hair
withstand a hot climate better than other men: on the contrary, experience
has taught him in making a selection of men for service on the coast of
Africa, to choose those with red hair. (62. 'Anthropological Review,'
Jan. 1866, p. xxi. Dr. Sharpe also says, with respect to India ('Man a
Special Creation,' 1873, p. 118), "that it has been noticed by some medical
officers that Europeans with light hair and florid complexions suffer less
from diseases of tropical countries than persons with dark hair and sallow
complexions; and, so far as I know, there appear to be good grounds for
this remark." On the other hand, Mr. Heddle, of Sierra Leone, "who has had
more clerks killed under him than any other man," by the climate of the
West African Coast (W. Reade, 'African Sketch Book,' vol. ii. p. 522),
holds a directly opposite view, as does Capt. Burton.) As far, therefore,
as these slight indications go, there seems no foundation for the
hypothesis, that blackness has resulted from the darker and darker
individuals having survived better during long exposure to fever-generating
miasma.
Dr. Sharpe remarks (63. 'Man a Special Creation,' 1873, p. 119.), that a
tropical sun, which burns and blisters a white skin, does not injure a
black one at all; and, as he adds, this is not due to habit in the
individual, for children only six or eight months old are often carried
about naked, and are not affected. I have been assured by a medical man,
that some years ago during each summer, but not during the winter, his
hands became marked with light brown patches, like, although larger than
freckles, and that these patches were never affected by sun-burning, whilst
the white parts of his skin have on several occasions been much inflamed
and blistered. With the lower animals there is, also, a constitutional
difference in liability to the action of the sun between those parts of the
skin clothed with white hair and other parts. (64. 'Variation of Animals
and Plants under Domestication,' vol. ii. pp. 336, 337.) Whether the
saving of the skin from being thus burnt is of sufficient importance to
account for a dark tint having been gradually acquired by man through
natural selection, I am unable to judge. If it be so, we should have to
assume that the natives of tropical America have lived there for a much
shorter time than the Negroes in Africa, or the Papuans in the southern
parts of the Malay archipelago, just as the lighter-coloured Hindoos have
resided in India for a shorter time than the darker aborigines of the
central and southern parts of the peninsula.
Although with our present knowledge we cannot account for the differences
of colour in the races of man, through any advantage thus gained, or from
the direct action of climate; yet we must not quite ignore the latter
agency, for there is good reason to believe that some inherited effect is
thus produced. (65. See, for instance, Quatrefages ('Revue des Cours
Scientifiques,' Oct. 10, 1868, p. 724) on the effects of residence in
Abyssinia and Arabia, and other analogous cases. Dr. Rolle ('Der Mensch,
seine Abstammung,' etc., 1865, s. 99) states, on the authority of Khanikof,
that the greater number of German families settled in Georgia, have
acquired in the course of two generations dark hair and eyes. Mr. D.
Forbes informs me that the Quichuas in the Andes vary greatly in colour,
according to the position of the valleys inhabited by them.)
We have seen in the second chapter that the conditions of life affect the
development of the bodily frame in a direct manner, and that the effects
are transmitted. Thus, as is generally admitted, the European settlers in
the United States undergo a slight but extraordinary rapid change of
appearance. Their bodies and limbs become elongated; and I hear from Col.
Bernys that during the late war in the United States, good evidence was
afforded of this fact by the ridiculous appearance presented by the German
regiments, when dressed in ready-made clothes manufactured for the American
market, and which were much too long for the men in every way. There is,
also, a considerable body of evidence shewing that in the Southern States
the house-slaves of the third generation present a markedly different
appearance from the field-slaves. (66. Harlan, 'Medical Researches,' p.
532. Quatrefages ('Unite de l'Espece Humaine,' 1861, p. 128) has collected
much evidence on this head.)
If, however, we look to the races of man as distributed over the world, we
must infer that their characteristic differences cannot be accounted for by
the direct action of different conditions of life, even after exposure to
them for an enormous period of time. The Esquimaux live exclusively on
animal food; they are clothed in thick fur, and are exposed to intense cold
and to prolonged darkness; yet they do not differ in any extreme degree
from the inhabitants of Southern China, who live entirely on vegetable
food, and are exposed almost naked to a hot, glaring climate. The
unclothed Fuegians live on the marine productions of their inhospitable
shores; the Botocudos of Brazil wander about the hot forests of the
interior and live chiefly on vegetable productions; yet these tribes
resemble each other so closely that the Fuegians on board the "Beagle" were
mistaken by some Brazilians for Botocudos. The Botocudos again, as well as
the other inhabitants of tropical America, are wholly different from the
Negroes who inhabit the opposite shores of the Atlantic, are exposed to a
nearly similar climate, and follow nearly the same habits of life.
Nor can the differences between the races of man be accounted for by the
inherited effects of the increased or decreased use of parts, except to a
quite insignificant degree. Men who habitually live in canoes, may have
their legs somewhat stunted; those who inhabit lofty regions may have their
chests enlarged; and those who constantly use certain sense-organs may have
the cavities in which they are lodged somewhat increased in size, and their
features consequently a little modified. With civilised nations, the
reduced size of the jaws from lessened use--the habitual play of different
muscles serving to express different emotions--and the increased size of
the brain from greater intellectual activity, have together produced a
considerable effect on their general appearance when compared with savages.
(67. See Prof. Schaaffhausen, translat., in 'Anthropological Review,' Oct.
1868, p. 429.) Increased bodily stature, without any corresponding
increase in the size of the brain, may (judging from the previously adduced
case of rabbits), have given to some races an elongated skull of the
dolichocephalic type.
Lastly, the little-understood principle of correlated development has
sometimes come into action, as in the case of great muscular development
and strongly projecting supra-orbital ridges. The colour of the skin and
hair are plainly correlated, as is the texture of the hair with its colour
in the Mandans of North America. (68. Mr. Catlin states ('N. American
Indians,' 3rd ed., 1842, vol. i. p. 49) that in the whole tribe of the
Mandans, about one in ten or twelve of the members, of all ages and both
sexes, have bright silvery grey hair, which is hereditary. Now this hair
is as coarse and harsh as that of a horse's mane, whilst the hair of other
colours is fine and soft.) The colour also of the skin, and the odour
emitted by it, are likewise in some manner connected. With the breeds of
sheep the number of hairs within a given space and the number of excretory
pores are related. (69. On the odour of the skin, Godron, 'Sur l'Espece,'
tom. ii. p. 217. On the pores in the skin, Dr. Wilckens, 'Die Aufgaben der
Landwirth. Zootechnik,' 1869, s. 7.) If we may judge from the analogy of
our domesticated animals, many modifications of structure in man probably
come under this principle of correlated development.
We have now seen that the external characteristic differences between the
races of man cannot be accounted for in a satisfactory manner by the direct
action of the conditions of life, nor by the effects of the continued use
of parts, nor through the principle of correlation. We are therefore led
to enquire whether slight individual differences, to which man is eminently
liable, may not have been preserved and augmented during a long series of
generations through natural selection. But here we are at once met by the
objection that beneficial variations alone can be thus preserved; and as
far as we are enabled to judge, although always liable to err on this head,
none of the differences between the races of man are of any direct or
special service to him. The intellectual and moral or social faculties
must of course be excepted from this remark. The great variability of all
the external differences between the races of man, likewise indicates that
they cannot be of much importance; for if important, they would long ago
have been either fixed and preserved, or eliminated. In this respect man
resembles those forms, called by naturalists protean or polymorphic, which
have remained extremely variable, owing, as it seems, to such variations
being of an indifferent nature, and to their having thus escaped the action
of natural selection.
We have thus far been baffled in all our attempts to account for the
differences between the races of man; but there remains one important
agency, namely Sexual Selection, which appears to have acted powerfully on
man, as on many other animals. I do not intend to assert that sexual
selection will account for all the differences between the races. An
unexplained residuum is left, about which we can only say, in our
ignorance, that as individuals are continually born with, for instance,
heads a little rounder or narrower, and with noses a little longer or
shorter, such slight differences might become fixed and uniform, if the
unknown agencies which induced them were to act in a more constant manner,
aided by long-continued intercrossing. Such variations come under the
provisional class, alluded to in our second chapter, which for want of a
better term are often called spontaneous. Nor do I pretend that the
effects of sexual selection can be indicated with scientific precision; but
it can be shewn that it would be an inexplicable fact if man had not been
modified by this agency, which appears to have acted powerfully on
innumerable animals. It can further be shewn that the differences between
the races of man, as in colour, hairiness, form of features, etc., are of a
kind which might have been expected to come under the influence of sexual
selection. But in order to treat this subject properly, I have found it
necessary to pass the whole animal kingdom in review. I have therefore
devoted to it the Second Part of this work. At the close I shall return to
man, and, after attempting to shew how far he has been modified through
sexual selection, will give a brief summary of the chapters in this First
Part.
NOTE ON THE RESEMBLANCES AND DIFFERENCES IN THE STRUCTURE AND THE
DEVELOPMENT OF THE BRAIN IN MAN AND APES BY PROFESSOR HUXLEY, F.R.S.
The controversy respecting the nature and the extent of the differences in
the structure of the brain in man and the apes, which arose some fifteen
years ago, has not yet come to an end, though the subject matter of the
dispute is, at present, totally different from what it was formerly. It
was originally asserted and re-asserted, with singular pertinacity, that
the brain of all the apes, even the highest, differs from that of man, in
the absence of such conspicuous structures as the posterior lobes of the
cerebral hemispheres, with the posterior cornu of the lateral ventricle and
the hippocampus minor, contained in those lobes, which are so obvious in
man.
But the truth that the three structures in question are as well developed
in apes' as in human brains, or even better; and that it is characteristic
of all the Primates (if we exclude the Lemurs) to have these parts well
developed, stands at present on as secure a basis as any proposition in
comparative anatomy. Moreover, it is admitted by every one of the long
series of anatomists who, of late years, have paid special attention to the
arrangement of the complicated sulci and gyri which appear upon the surface
of the cerebral hemispheres in man and the higher apes, that they are
disposed after the very same pattern in him, as in them. Every principal
gyrus and sulcus of a chimpanzee's brain is clearly represented in that of
a man, so that the terminology which applies to the one answers for the
other. On this point there is no difference of opinion. Some years since,
Professor Bischoff published a memoir (70. 'Die Grosshirn-Windungen des
Menschen;' 'Abhandlungen der K. Bayerischen Akademie,' B. x. 1868.) on the
cerebral convolutions of man and apes; and as the purpose of my learned
colleague was certainly not to diminish the value of the differences
between apes and men in this respect, I am glad to make a citation from
him.
"That the apes, and especially the orang, chimpanzee and gorilla, come very
close to man in their organisation, much nearer than to any other animal,
is a well known fact, disputed by nobody. Looking at the matter from the
point of view of organisation alone, no one probably would ever have
disputed the view of Linnaeus, that man should be placed, merely as a
peculiar species, at the head of the mammalia and of those apes. Both
shew, in all their organs, so close an affinity, that the most exact
anatomical investigation is needed in order to demonstrate those
differences which really exist. So it is with the brains. The brains of
man, the orang, the chimpanzee, the gorilla, in spite of all the important
differences which they present, come very close to one another" (loc. cit.
p. 101).
There remains, then, no dispute as to the resemblance in fundamental
characters, between the ape's brain and man's: nor any as to the
wonderfully close similarity between the chimpanzee, orang and man, in even
the details of the arrangement of the gyri and sulci of the cerebral
hemispheres. Nor, turning to the differences between the brains of the
highest apes and that of man, is there any serious question as to the
nature and extent of these differences. It is admitted that the man's
cerebral hemispheres are absolutely and relatively larger than those of the
orang and chimpanzee; that his frontal lobes are less excavated by the
upward protrusion of the roof of the orbits; that his gyri and sulci are,
as a rule, less symmetrically disposed, and present a greater number of
secondary plications. And it is admitted that, as a rule, in man, the
temporo-occipital or "external perpendicular" fissure, which is usually so
strongly marked a feature of the ape's brain is but faintly marked. But it
is also clear, that none of these differences constitutes a sharp
demarcation between the man's and the ape's brain. In respect to the
external perpendicular fissure of Gratiolet, in the human brain for
instance, Professor Turner remarks: (71. 'Convolutions of the Human
Cerebrum Topographically Considered,' 1866, p. 12.)
"In some brains it appears simply as an indentation of the margin of the
hemisphere, but, in others, it extends for some distance more or less
transversely outwards. I saw it in the right hemisphere of a female brain
pass more than two inches outwards; and on another specimen, also the right
hemisphere, it proceeded for four-tenths of an inch outwards, and then
extended downwards, as far as the lower margin of the outer surface of the
hemisphere. The imperfect definition of this fissure in the majority of
human brains, as compared with its remarkable distinctness in the brain of
most Quadrumana, is owing to the presence, in the former, of certain
superficial, well marked, secondary convolutions which bridge it over and
connect the parietal with the occipital lobe. The closer the first of
these bridging gyri lies to the longitudinal fissure, the shorter is the
external parieto-occipital fissure" (loc. cit. p. 12).
The obliteration of the external perpendicular fissure of Gratiolet,
therefore, is not a constant character of the human brain. On the other
hand, its full development is not a constant character of the higher ape's
brain. For, in the chimpanzee, the more or less extensive obliteration of
the external perpendicular sulcus by "bridging convolutions," on one side
or the other, has been noted over and over again by Prof. Rolleston, Mr.
Marshall, M. Broca and Professor Turner. At the conclusion of a special
paper on this subject the latter writes: (72. Notes more especially on
the bridging convolutions in the Brain of the Chimpanzee, 'Proceedings of
the Royal Society of Edinburgh,' 1865-6.)
"The three specimens of the brain of a chimpanzee, just described, prove,
that the generalisation which Gratiolet has attempted to draw of the
complete absence of the first connecting convolution and the concealment of
the second, as essentially characteristic features in the brain of this
animal, is by no means universally applicable. In only one specimen did
the brain, in these particulars, follow the law which Gratiolet has
expressed. As regards the presence of the superior bridging convolution, I
am inclined to think that it has existed in one hemisphere, at least, in a
majority of the brains of this animal which have, up to this time, been
figured or described. The superficial position of the second bridging
convolution is evidently less frequent, and has as yet, I believe, only
been seen in the brain (A) recorded in this communication. The
asymmetrical arrangement in the convolutions of the two hemispheres, which
previous observers have referred to in their descriptions, is also well
illustrated in these specimens" (pp. 8, 9).
Even were the presence of the temporo-occipital, or external perpendicular,
sulcus, a mark of distinction between the higher apes and man, the value of
such a distinctive character would be rendered very doubtful by the
structure of the brain in the Platyrrhine apes. In fact, while the
temporo-occipital is one of the most constant of sulci in the Catarrhine,
or Old World, apes, it is never very strongly developed in the New World
apes; it is absent in the smaller Platyrrhini; rudimentary in Pithecia (73.
Flower, 'On the Anatomy of Pithecia Monachus,' 'Proceedings of the
Zoological Society,' 1862.); and more or less obliterated by bridging
convolutions in Ateles.
A character which is thus variable within the limits of a single group can
have no great taxonomic value.
It is further established, that the degree of asymmetry of the convolution
of the two sides in the human brain is subject to much individual
variation; and that, in those individuals of the Bushman race who have been
examined, the gyri and sulci of the two hemispheres are considerably less
complicated and more symmetrical than in the European brain, while, in some
individuals of the chimpanzee, their complexity and asymmetry become
notable. This is particularly the case in the brain of a young male
chimpanzee figured by M. Broca. ('L'ordre des Primates,' p. 165, fig. 11.)
Again, as respects the question of absolute size, it is established that
the difference between the largest and the smallest healthy human brain is
greater than the difference between the smallest healthy human brain and
the largest chimpanzee's or orang's brain.
Moreover, there is one circumstance in which the orang's and chimpanzee's
brains resemble man's, but in which they differ from the lower apes, and
that is the presence of two corpora candicantia--the Cynomorpha having but
one.
In view of these facts I do not hesitate in this year 1874, to repeat and
insist upon the proposition which I enunciated in 1863: (74. 'Man's Place
in Nature,' p. 102.)
"So far as cerebral structure goes, therefore, it is clear that man differs
less from the chimpanzee or the orang, than these do even from the monkeys,
and that the difference between the brain of the chimpanzee and of man is
almost insignificant when compared with that between the chimpanzee brain
and that of a Lemur."
In the paper to which I have referred, Professor Bischoff does not deny the
second part of this statement, but he first makes the irrelevant remark
that it is not wonderful if the brains of an orang and a Lemur are very
different; and secondly, goes on to assert that, "If we successively
compare the brain of a man with that of an orang; the brain of this with
that of a chimpanzee; of this with that of a gorilla, and so on of a
Hylobates, Semnopithecus, Cynocephalus, Cercopithecus, Macacus, Cebus,
Callithrix, Lemur, Stenops, Hapale, we shall not meet with a greater, or
even as great a, break in the degree of development of the convolutions, as
we find between the brain of a man and that of an orang or chimpanzee."
To which I reply, firstly, that whether this assertion be true or false, it
has nothing whatever to do with the proposition enunciated in 'Man's Place
in Nature,' which refers not to the development of the convolutions alone,
but to the structure of the whole brain. If Professor Bischoff had taken
the trouble to refer to p. 96 of the work he criticises, in fact, he would
have found the following passage: "And it is a remarkable circumstance
that though, so far as our present knowledge extends, there IS one true
structural break in the series of forms of Simian brains, this hiatus does
not lie between man and the manlike apes, but between the lower and the
lowest Simians, or in other words, between the Old and New World apes and
monkeys and the Lemurs. Every Lemur which has yet been examined, in fact,
has its cerebellum partially visible from above; and its posterior lobe,
with the contained posterior cornu and hippocampus minor, more or less
rudimentary. Every marmoset, American monkey, Old World monkey, baboon or
manlike ape, on the contrary, has its cerebellum entirely hidden,
posteriorly, by the cerebral lobes, and possesses a large posterior cornu
with a well-developed hippocampus minor."
This statement was a strictly accurate account of what was known when it
was made; and it does not appear to me to be more than apparently weakened
by the subsequent discovery of the relatively small development of the
posterior lobes in the Siamang and in the Howling monkey. Notwithstanding
the exceptional brevity of the posterior lobes in these two species, no one
will pretend that their brains, in the slightest degree, approach those of
the Lemurs. And if, instead of putting Hapale out of its natural place, as
Professor Bischoff most unaccountably does, we write the series of animals
he has chosen to mention as follows: Homo, Pithecus, Troglodytes,
Hylobates, Semnopithecus, Cynocephalus, Cercopithecus, Macacus, Cebus,
Callithrix, Hapale, Lemur, Stenops, I venture to reaffirm that the great
break in this series lies between Hapale and Lemur, and that this break is
considerably greater than that between any other two terms of that series.
Professor Bischoff ignores the fact that long before he wrote, Gratiolet
had suggested the separation of the Lemurs from the other Primates on the
very ground of the difference in their cerebral characters; and that
Professor Flower had made the following observations in the course of his
description of the brain of the Javan Loris: (75. 'Transactions of the
Zoological Society,' vol. v. 1862.)
"And it is especially remarkable that, in the development of the posterior
lobes, there is no approximation to the Lemurine, short hemisphered brain,
in those monkeys which are commonly supposed to approach this family in
other respects, viz. the lower members of the Platyrrhine group."
So far as the structure of the adult brain is concerned, then, the very
considerable additions to our knowledge, which have been made by the
researches of so many investigators, during the past ten years, fully
justify the statement which I made in 1863. But it has been said, that,
admitting the similarity between the adult brains of man and apes, they are
nevertheless, in reality, widely different, because they exhibit
fundamental differences in the mode of their development. No one would be
more ready than I to admit the force of this argument, if such fundamental
differences of development really exist. But I deny that they do exist.
On the contrary, there is a fundamental agreement in the development of the
brain in men and apes.
Gratiolet originated the statement that there is a fundamental difference
in the development of the brains of apes and that of man--consisting in
this; that, in the apes, the sulci which first make their appearance are
situated on the posterior region of the cerebral hemispheres, while, in the
human foetus, the sulci first become visible on the frontal lobes. (76.
"Chez tous les singes, les plis posterieurs se developpent les premiers;
les plis anterieurs se developpent plus tard, aussi la vertebre occipitale
et la parietale sont-elles relativement tres-grandes chez le foetus.
L'Homme presente une exception remarquable quant a l'epoque de l'apparition
des plis frontaux, qui sont les premiers indiques; mais le developpement
general du lobe frontal, envisage seulement par rapport a son volume, suit
les memes lois que dans les singes:" Gratiolet, 'Memoire sur les plis
cerebres de l'Homme et des Primateaux,' p. 39, Tab. iv, fig. 3.)
This general statement is based upon two observations, the one of a Gibbon
almost ready to be born, in which the posterior gyri were "well developed,"
while those of the frontal lobes were "hardly indicated" (77. Gratiolet's
words are (loc. cit. p. 39): "Dans le foetus dont il s'agit les plis
cerebraux posterieurs sont bien developpes, tandis que les plis du lobe
frontal sont a peine indiques." The figure, however (Pl. iv, fig. 3),
shews the fissure of Rolando, and one of the frontal sulci plainly enough.
Nevertheless, M. Alix, in his 'Notice sur les travaux anthropologiques de
Gratiolet' ('Mem. de la Societe d'Anthropologie de Paris,' 1868, page 32),
writes thus: "Gratiolet a eu entre les mains le cerveau d'un foetus de
Gibbon, singe eminemment superieur, et tellement rapproche de l'orang, que
des naturalistes tres-competents l'ont range parmi les anthropoides. M.
Huxley, par exemple, n'hesite pas sur ce point. Eh bien, c'est sur le
cerveau d'un foetus de Gibbon que Gratiolet a vu LES CIRCONVOLUTIONS DU
LOBE TEMPORO-SPHENOIDAL DEJA DEVELOPPEES LORSQU'IL N'EXISTENT PAS ENCORE DE
PLIS SUR LE LOBE FRONTAL. Il etait donc bien autorise a dire que, chez
l'homme les circonvolutions apparaissent d'a en w, tandis que chez les
singes elles se developpent d'w en a."), and the other of a human foetus at
the 22nd or 23rd week of uterogestation, in which Gratiolet notes that the
insula was uncovered, but that nevertheless "des incisures sement de lobe
anterieur, une scissure peu profonde indique la separation du lobe
occipital, tres-reduit, d'ailleurs des cette epoque. Le reste de la
surface cerebrale est encore absolument lisse."
Three views of this brain are given in Plate II, figs. 1, 2, 3, of the work
cited, shewing the upper, lateral and inferior views of the hemispheres,
but not the inner view. It is worthy of note that the figure by no means
bears out Gratiolet's description, inasmuch as the fissure (antero-
temporal) on the posterior half of the face of the hemisphere is more
marked than any of those vaguely indicated in the anterior half. If the
figure is correct, it in no way justifies Gratiolet's conclusion: "Il y a
donc entre ces cerveaux [those of a Callithrix and of a Gibbon] et celui du
foetus humain une difference fondamental. Chez celui-ci, longtemps avant
que les plis temporaux apparaissent, les plis frontaux, ESSAYENT
d'exister."
Since Gratiolet's time, however, the development of the gyri and sulci of
the brain has been made the subject of renewed investigation by Schmidt,
Bischoff, Pansch (78. 'Ueber die typische Anordnung der Furchen und
Windungen auf den Grosshirn-Hemispharen des Menschen und der Affen,'
'Archiv fur Anthropologie,' iii. 1868.), and more particularly by Ecker
(79. 'Zur Entwicklungs Geschichte der Furchen und Windungen der Grosshirn-
Hemispharen im Foetus des Menschen.' 'Archiv fur Anthropologie,' iii.
1868.), whose work is not only the latest, but by far the most complete,
memoir on the subject.
The final results of their inquiries may be summed up as follows:--
1. In the human foetus, the sylvian fissure is formed in the course of the
third month of uterogestation. In this, and in the fourth month, the
cerebral hemispheres are smooth and rounded (with the exception of the
sylvian depression), and they project backwards far beyond the cerebellum.
2. The sulci, properly so called, begin to appear in the interval between
the end of the fourth and the beginning of the sixth month of foetal life,
but Ecker is careful to point out that, not only the time, but the order,
of their appearance is subject to considerable individual variation. In no
case, however, are either the frontal or the temporal sulci the earliest.
The first which appears, in fact, lies on the inner face of the hemisphere
(whence doubtless Gratiolet, who does not seem to have examined that face
in his foetus, overlooked it), and is either the internal perpendicular
(occipito-parietal), or the calcarine sulcus, these two being close
together and eventually running into one another. As a rule the occipito-
parietal is the earlier of the two.
3. At the latter part of this period, another sulcus, the "posterio-
parietal," or "Fissure of Rolando" is developed, and it is followed, in the
course of the sixth month, by the other principal sulci of the frontal,
parietal, temporal and occipital lobes. There is, however, no clear
evidence that one of these constantly appears before the other; and it is
remarkable that, in the brain at the period described and figured by Ecker
(loc. cit. pp. 212-213, Taf. II, figs. 1, 2, 3, 4), the antero-temporal
sulcus (scissure parallele) so characteristic of the ape's brain, is as
well, if not better developed than the fissure of Rolando, and is much more
marked than the proper frontal sulci.
Taking the facts as they now stand, it appears to me that the order of the
appearance of the sulci and gyri in the foetal human brain is in perfect
harmony with the general doctrine of evolution, and with the view that man
has been evolved from some ape-like form; though there can be no doubt that
form was, in many respects, different from any member of the Primates now
living.
Von Baer taught us, half a century ago, that, in the course of their
development, allied animals put on at first, the characters of the greater
groups to which they belong, and, by degrees, assume those which restrict
them within the limits of their family, genus, and species; and he proved,
at the same time, that no developmental stage of a higher animal is
precisely similar to the adult condition of any lower animal. It is quite
correct to say that a frog passes through the condition of a fish, inasmuch
as at one period of its life the tadpole has all the characters of a fish,
and if it went no further, would have to be grouped among fishes. But it
is equally true that a tadpole is very different from any known fish.
In like manner, the brain of a human foetus, at the fifth month, may
correctly be said to be, not only the brain of an ape, but that of an
Arctopithecine or marmoset-like ape; for its hemispheres, with their great
posterior lobster, and with no sulci but the sylvian and the calcarine,
present the characteristics found only in the group of the Arctopithecine
Primates. But it is equally true, as Gratiolet remarks, that, in its
widely open sylvian fissure, it differs from the brain of any actual
marmoset. No doubt it would be much more similar to the brain of an
advanced foetus of a marmoset. But we know nothing whatever of the
development of the brain in the marmosets. In the Platyrrhini proper, the
only observation with which I am acquainted is due to Pansch, who found in
the brain of a foetal Cebus Apella, in addition to the sylvian fissure and
the deep calcarine fissure, only a very shallow antero-temporal fissure
(scissure parallele of Gratiolet).
Now this fact, taken together with the circumstance that the antero-
temporal sulcus is present in such Platyrrhini as the Saimiri, which
present mere traces of sulci on the anterior half of the exterior of the
cerebral hemispheres, or none at all, undoubtedly, so far as it goes,
affords fair evidence in favour of Gratiolet's hypothesis, that the
posterior sulci appear before the anterior, in the brains of the
Platyrrhini. But, it by no means follows, that the rule which may hold
good for the Platyrrhini extends to the Catarrhini. We have no information
whatever respecting the development of the brain in the Cynomorpha; and, as
regards the Anthropomorpha, nothing but the account of the brain of the
Gibbon, near birth, already referred to. At the present moment there is
not a shadow of evidence to shew that the sulci of a chimpanzee's, or
orang's, brain do not appear in the same order as a man's.
Gratiolet opens his preface with the aphorism: "Il est dangereux dans les
sciences de conclure trop vite." I fear he must have forgotten this sound
maxim by the time he had reached the discussion of the differences between
men and apes, in the body of his work. No doubt, the excellent author of
one of the most remarkable contributions to the just understanding of the
mammalian brain which has ever been made, would have been the first to
admit the insufficiency of his data had he lived to profit by the advance
of inquiry. The misfortune is that his conclusions have been employed by
persons incompetent to appreciate their foundation, as arguments in favour
of obscurantism. (80. For example, M. l'Abbe Lecomte in his terrible
pamphlet, 'Le Darwinisme et l'origine de l'Homme,' 1873.)
But it is important to remark that, whether Gratiolet was right or wrong in
his hypothesis respecting the relative order of appearance of the temporal
and frontal sulci, the fact remains; that before either temporal or frontal
sulci, appear, the foetal brain of man presents characters which are found
only in the lowest group of the Primates (leaving out the Lemurs); and that
this is exactly what we should expect to be the case, if man has resulted
from the gradual modification of the same form as that from which the other
Primates have sprung.
PART II. SEXUAL SELECTION.
CHAPTER VIII.
PRINCIPLES OF SEXUAL SELECTION.
Secondary sexual characters--Sexual selection--Manner of action--Excess of
males--Polygamy--The male alone generally modified through sexual
selection--Eagerness of the male--Variability of the male--Choice exerted
by the female--Sexual compared with natural selection--Inheritance, at
corresponding periods of life, at corresponding seasons of the year, and as
limited by sex--Relations between the several forms of inheritance--Causes
why one sex and the young are not modified through sexual selection--
Supplement on the proportional numbers of the two sexes throughout the
animal kingdom--The proportion of the sexes in relation to natural
selection.
With animals which have their sexes separated, the males necessarily differ
from the females in their organs of reproduction; and these are the primary
sexual characters. But the sexes often differ in what Hunter has called
secondary sexual characters, which are not directly connected with the act
of reproduction; for instance, the male possesses certain organs of sense
or locomotion, of which the female is quite destitute, or has them more
highly-developed, in order that he may readily find or reach her; or again
the male has special organs of prehension for holding her securely. These
latter organs, of infinitely diversified kinds, graduate into those which
are commonly ranked as primary, and in some cases can hardly be
distinguished from them; we see instances of this in the complex appendages
at the apex of the abdomen in male insects. Unless indeed we confine the
term "primary" to the reproductive glands, it is scarcely possible to
decide which ought to be called primary and which secondary.
The female often differs from the male in having organs for the nourishment
or protection of her young, such as the mammary glands of mammals, and the
abdominal sacks of the marsupials. In some few cases also the male
possesses similar organs, which are wanting in the female, such as the
receptacles for the ova in certain male fishes, and those temporarily
developed in certain male frogs. The females of most bees are provided
with a special apparatus for collecting and carrying pollen, and their
ovipositor is modified into a sting for the defence of the larvae and the
community. Many similar cases could be given, but they do not here concern
us. There are, however, other sexual differences quite unconnected with
the primary reproductive organs, and it is with these that we are more
especially concerned--such as the greater size, strength, and pugnacity of
the male, his weapons of offence or means of defence against rivals, his
gaudy colouring and various ornaments, his power of song, and other such
characters.
Besides the primary and secondary sexual differences, such as the
foregoing, the males and females of some animals differ in structures
related to different habits of life, and not at all, or only indirectly, to
the reproductive functions. Thus the females of certain flies (Culicidae
and Tabanidae) are blood-suckers, whilst the males, living on flowers, have
mouths destitute of mandibles. (1. Westwood, 'Modern Classification of
Insects,' vol. ii. 1840, p. 541. For the statement about Tanais, mentioned
below, I am indebted to Fritz Muller.) The males of certain moths and of
some crustaceans (e.g. Tanais) have imperfect, closed mouths, and cannot
feed. The complemental males of certain Cirripedes live like epiphytic
plants either on the female or the hermaphrodite form, and are destitute of
a mouth and of prehensile limbs. In these cases it is the male which has
been modified, and has lost certain important organs, which the females
possess. In other cases it is the female which has lost such parts; for
instance, the female glow-worm is destitute of wings, as also are many
female moths, some of which never leave their cocoons. Many female
parasitic crustaceans have lost their natatory legs. In some weevil-
beetles (Curculionidae) there is a great difference between the male and
female in the length of the rostrum or snout (2. Kirby and Spence,
'Introduction to Entomology,' vol. iii. 1826, p. 309.); but the meaning of
this and of many analogous differences, is not at all understood.
Differences of structure between the two sexes in relation to different
habits of life are generally confined to the lower animals; but with some
few birds the beak of the male differs from that of the female. In the
Huia of New Zealand the difference is wonderfully great, and we hear from
Dr. Buller (3. 'Birds of New Zealand,' 1872, p. 66.) that the male uses
his strong beak in chiselling the larvae of insects out of decayed wood,
whilst the female probes the softer parts with her far longer, much curved
and pliant beak: and thus they mutually aid each other. In most cases,
differences of structure between the sexes are more or less directly
connected with the propagation of the species: thus a female, which has to
nourish a multitude of ova, requires more food than the male, and
consequently requires special means for procuring it. A male animal, which
lives for a very short time, might lose its organs for procuring food
through disuse, without detriment; but he would retain his locomotive
organs in a perfect state, so that he might reach the female. The female,
on the other hand, might safely lose her organs for flying, swimming, or
walking, if she gradually acquired habits which rendered such powers
useless.
We are, however, here concerned only with sexual selection. This depends
on the advantage which certain individuals have over others of the same sex
and species solely in respect of reproduction. When, as in the cases above
mentioned, the two sexes differ in structure in relation to different
habits of life, they have no doubt been modified through natural selection,
and by inheritance limited to one and the same sex. So again the primary
sexual organs, and those for nourishing or protecting the young, come under
the same influence; for those individuals which generated or nourished
their offspring best, would leave, ceteris paribus, the greatest number to
inherit their superiority; whilst those which generated or nourished their
offspring badly, would leave but few to inherit their weaker powers. As
the male has to find the female, he requires organs of sense and
locomotion, but if these organs are necessary for the other purposes of
life, as is generally the case, they will have been developed through
natural selection. When the male has found the female, he sometimes
absolutely requires prehensile organs to hold her; thus Dr. Wallace informs
me that the males of certain moths cannot unite with the females if their
tarsi or feet are broken. The males of many oceanic crustaceans, when
adult, have their legs and antennae modified in an extraordinary manner for
the prehension of the female; hence we may suspect that it is because these
animals are washed about by the waves of the open sea, that they require
these organs in order to propagate their kind, and if so, their development
has been the result of ordinary or natural selection. Some animals
extremely low in the scale have been modified for this same purpose; thus
the males of certain parasitic worms, when fully grown, have the lower
surface of the terminal part of their bodies roughened like a rasp, and
with this they coil round and permanently hold the females. (4. M.
Perrier advances this case ('Revue Scientifique,' Feb. 1, 1873, p. 865) as
one fatal to the belief in sexual election, inasmuch as he supposes that I
attribute all the differences between the sexes to sexual selection. This
distinguished naturalist, therefore, like so many other Frenchmen, has not
taken the trouble to understand even the first principles of sexual
selection. An English naturalist insists that the claspers of certain male
animals could not have been developed through the choice of the female!
Had I not met with this remark, I should not have thought it possible for
any one to have read this chapter and to have imagined that I maintain that
the choice of the female had anything to do with the development of the
prehensile organs in the male.)
When the two sexes follow exactly the same habits of life, and the male has
the sensory or locomotive organs more highly developed than those of the
female, it may be that the perfection of these is indispensable to the male
for finding the female; but in the vast majority of cases, they serve only
to give one male an advantage over another, for with sufficient time, the
less well-endowed males would succeed in pairing with the females; and
judging from the structure of the female, they would be in all other
respects equally well adapted for their ordinary habits of life. Since in
such cases the males have acquired their present structure, not from being
better fitted to survive in the struggle for existence, but from having
gained an advantage over other males, and from having transmitted this
advantage to their male offspring alone, sexual selection must here have
come into action. It was the importance of this distinction which led me
to designate this form of selection as Sexual Selection. So again, if the
chief service rendered to the male by his prehensile organs is to prevent
the escape of the female before the arrival of other males, or when
assaulted by them, these organs will have been perfected through sexual
selection, that is by the advantage acquired by certain individuals over
their rivals. But in most cases of this kind it is impossible to
distinguish between the effects of natural and sexual selection. Whole
chapters could be filled with details on the differences between the sexes
in their sensory, locomotive, and prehensile organs. As, however, these
structures are not more interesting than others adapted for the ordinary
purposes of life I shall pass them over almost entirely, giving only a few
instances under each class.
There are many other structures and instincts which must have been
developed through sexual selection--such as the weapons of offence and the
means of defence of the males for fighting with and driving away their
rivals--their courage and pugnacity--their various ornaments--their
contrivances for producing vocal or instrumental music--and their glands
for emitting odours, most of these latter structures serving only to allure
or excite the female. It is clear that these characters are the result of
sexual and not of ordinary selection, since unarmed, unornamented, or
unattractive males would succeed equally well in the battle for life and in
leaving a numerous progeny, but for the presence of better endowed males.
We may infer that this would be the case, because the females, which are
unarmed and unornamented, are able to survive and procreate their kind.
Secondary sexual characters of the kind just referred to, will be fully
discussed in the following chapters, as being in many respects interesting,
but especially as depending on the will, choice, and rivalry of the
individuals of either sex. When we behold two males fighting for the
possession of the female, or several male birds displaying their gorgeous
plumage, and performing strange antics before an assembled body of females,
we cannot doubt that, though led by instinct, they know what they are
about, and consciously exert their mental and bodily powers.
Just as man can improve the breeds of his game-cocks by the selection of
those birds which are victorious in the cockpit, so it appears that the
strongest and most vigorous males, or those provided with the best weapons,
have prevailed under nature, and have led to the improvement of the natural
breed or species. A slight degree of variability leading to some
advantage, however slight, in reiterated deadly contests would suffice for
the work of sexual selection; and it is certain that secondary sexual
characters are eminently variable. Just as man can give beauty, according
to his standard of taste, to his male poultry, or more strictly can modify
the beauty originally acquired by the parent species, can give to the
Sebright bantam a new and elegant plumage, an erect and peculiar carriage--
so it appears that female birds in a state of nature, have by a long
selection of the more attractive males, added to their beauty or other
attractive qualities. No doubt this implies powers of discrimination and
taste on the part of the female which will at first appear extremely
improbable; but by the facts to be adduced hereafter, I hope to be able to
shew that the females actually have these powers. When, however, it is
said that the lower animals have a sense of beauty, it must not be supposed
that such sense is comparable with that of a cultivated man, with his
multiform and complex associated ideas. A more just comparison would be
between the taste for the beautiful in animals, and that in the lowest
savages, who admire and deck themselves with any brilliant, glittering, or
curious object.
From our ignorance on several points, the precise manner in which sexual
selection acts is somewhat uncertain. Nevertheless if those naturalists
who already believe in the mutability of species, will read the following
chapters, they will, I think, agree with me, that sexual selection has
played an important part in the history of the organic world. It is
certain that amongst almost all animals there is a struggle between the
males for the possession of the female. This fact is so notorious that it
would be superfluous to give instances. Hence the females have the
opportunity of selecting one out of several males, on the supposition that
their mental capacity suffices for the exertion of a choice. In many cases
special circumstances tend to make the struggle between the males
particularly severe. Thus the males of our migratory birds generally
arrive at their places of breeding before the females, so that many males
are ready to contend for each female. I am informed by Mr. Jenner Weir,
that the bird-catchers assert that this is invariably the case with the
nightingale and blackcap, and with respect to the latter he can himself
confirm the statement.
Mr. Swaysland of Brighton has been in the habit, during the last forty
years, of catching our migratory birds on their first arrival, and he has
never known the females of any species to arrive before their males.
During one spring he shot thirty-nine males of Ray's wagtail (Budytes Raii)
before he saw a single female. Mr. Gould has ascertained by the dissection
of those snipes which arrive the first in this country, that the males come
before the females. And the like holds good with most of the migratory
birds of the United States. (5. J.A. Allen, on the 'Mammals and Winter
Birds of Florida,' Bulletin of Comparative Zoology, Harvard College, p.
268.) The majority of the male salmon in our rivers, on coming up from the
sea, are ready to breed before the females. So it appears to be with frogs
and toads. Throughout the great class of insects the males almost always
are the first to emerge from the pupal state, so that they generally abound
for a time before any females can be seen. (6. Even with those plants in
which the sexes are separate, the male flowers are generally mature before
the female. As first shewn by C.K. Sprengel, many hermaphrodite plants are
dichogamous; that is, their male and female organs are not ready at the
same time, so that they cannot be self-fertilised. Now in such flowers,
the pollen is in general matured before the stigma, though there are
exceptional cases in which the female organs are beforehand.) The cause of
this difference between the males and females in their periods of arrival
and maturity is sufficiently obvious. Those males which annually first
migrated into any country, or which in the spring were first ready to
breed, or were the most eager, would leave the largest number of offspring;
and these would tend to inherit similar instincts and constitutions. It
must be borne in mind that it would have been impossible to change very
materially the time of sexual maturity in the females, without at the same
time interfering with the period of the production of the young--a period
which must be determined by the seasons of the year. On the whole there
can be no doubt that with almost all animals, in which the sexes are
separate, there is a constantly recurrent struggle between the males for
the possession of the females.
Our difficulty in regard to sexual selection lies in understanding how it
is that the males which conquer other males, or those which prove the most
attractive to the females, leave a greater number of offspring to inherit
their superiority than their beaten and less attractive rivals. Unless
this result does follow, the characters which give to certain males an
advantage over others, could not be perfected and augmented through sexual
selection. When the sexes exist in exactly equal numbers, the worst-
endowed males will (except where polygamy prevails), ultimately find
females, and leave as many offspring, as well fitted for their general
habits of life, as the best-endowed males. From various facts and
considerations, I formerly inferred that with most animals, in which
secondary sexual characters are well developed, the males considerably
exceeded the females in number; but this is not by any means always true.
If the males were to the females as two to one, or as three to two, or even
in a somewhat lower ratio, the whole affair would be simple; for the
better-armed or more attractive males would leave the largest number of
offspring. But after investigating, as far as possible, the numerical
proportion of the sexes, I do not believe that any great inequality in
number commonly exists. In most cases sexual selection appears to have
been effective in the following manner.
Let us take any species, a bird for instance, and divide the females
inhabiting a district into two equal bodies, the one consisting of the more
vigorous and better-nourished individuals, and the other of the less
vigorous and healthy. The former, there can be little doubt, would be
ready to breed in the spring before the others; and this is the opinion of
Mr. Jenner Weir, who has carefully attended to the habits of birds during
many years. There can also be no doubt that the most vigorous, best-
nourished and earliest breeders would on an average succeed in rearing the
largest number of fine offspring. (7. Here is excellent evidence on the
character of the offspring from an experienced ornithologist. Mr. J.A.
Allen, in speaking ('Mammals and Winter Birds of E. Florida,' p. 229) of
the later broods, after the accidental destruction of the first, says, that
these "are found to be smaller and paler-coloured than those hatched
earlier in the season. In cases where several broods are reared each year,
as a general rule the birds of the earlier broods seem in all respects the
most perfect and vigorous.") The males, as we have seen, are generally
ready to breed before the females; the strongest, and with some species the
best armed of the males, drive away the weaker; and the former would then
unite with the more vigorous and better-nourished females, because they are
the first to breed. (8. Hermann Muller has come to this same conclusion
with respect to those female bees which are the first to emerge from the
pupa each year. See his remarkable essay, 'Anwendung der Darwin'schen
Lehre auf Bienen,' 'Verh. d. V. Jahrg.' xxix. p. 45.) Such vigorous pairs
would surely rear a larger number of offspring than the retarded females,
which would be compelled to unite with the conquered and less powerful
males, supposing the sexes to be numerically equal; and this is all that is
wanted to add, in the course of successive generations, to the size,
strength and courage of the males, or to improve their weapons.
But in very many cases the males which conquer their rivals, do not obtain
possession of the females, independently of the choice of the latter. The
courtship of animals is by no means so simple and short an affair as might
be thought. The females are most excited by, or prefer pairing with, the
more ornamented males, or those which are the best songsters, or play the
best antics; but it is obviously probable that they would at the same time
prefer the more vigorous and lively males, and this has in some cases been
confirmed by actual observation. (9. With respect to poultry, I have
received information, hereafter to be given, to this effect. Even birds,
such as pigeons, which pair for life, the female, as I hear from Mr. Jenner
Weir, will desert her mate if he is injured or grows weak.) Thus the more
vigorous females, which are the first to breed, will have the choice of
many males; and though they may not always select the strongest or best
armed, they will select those which are vigorous and well armed, and in
other respects the most attractive. Both sexes, therefore, of such early
pairs would as above explained, have an advantage over others in rearing
offspring; and this apparently has sufficed during a long course of
generations to add not only to the strength and fighting powers of the
males, but likewise to their various ornaments or other attractions.
In the converse and much rarer case of the males selecting particular
females, it is plain that those which were the most vigorous and had
conquered others, would have the freest choice; and it is almost certain
that they would select vigorous as well as attractive females. Such pairs
would have an advantage in rearing offspring, more especially if the male
had the power to defend the female during the pairing-season as occurs with
some of the higher animals, or aided her in providing for the young. The
same principles would apply if each sex preferred and selected certain
individuals of the opposite sex; supposing that they selected not only the
more attractive, but likewise the more vigorous individuals.
NUMERICAL PROPORTION OF THE TWO SEXES.
I have remarked that sexual selection would be a simple affair if the males
were considerably more numerous than the females. Hence I was led to
investigate, as far as I could, the proportions between the two sexes of as
many animals as possible; but the materials are scanty. I will here give
only a brief abstract of the results, retaining the details for a
supplementary discussion, so as not to interfere with the course of my
argument. Domesticated animals alone afford the means of ascertaining the
proportional numbers at birth; but no records have been specially kept for
this purpose. By indirect means, however, I have collected a considerable
body of statistics, from which it appears that with most of our domestic
animals the sexes are nearly equal at birth. Thus 25,560 births of race-
horses have been recorded during twenty-one years, and the male births were
to the female births as 99.7 to 100. In greyhounds the inequality is
greater than with any other animal, for out of 6878 births during twelve
years, the male births were to the female as 110.1 to 100. It is, however,
in some degree doubtful whether it is safe to infer that the proportion
would be the same under natural conditions as under domestication; for
slight and unknown differences in the conditions affect the proportion of
the sexes. Thus with mankind, the male births in England are as 104.5, in
Russia as 108.9, and with the Jews of Livonia as 120, to 100 female births.
But I shall recur to this curious point of the excess of male births in the
supplement to this chapter. At the Cape of Good Hope, however, male
children of European extraction have been born during several years in the
proportion of between 90 and 99 to 100 female children.
For our present purpose we are concerned with the proportions of the sexes,
not only at birth, but also at maturity, and this adds another element of
doubt; for it is a well-ascertained fact that with man the number of males
dying before or during birth, and during the first two years of infancy, is
considerably larger than that of females. So it almost certainly is with
male lambs, and probably with some other animals. The males of some
species kill one another by fighting; or they drive one another about until
they become greatly emaciated. They must also be often exposed to various
dangers, whilst wandering about in eager search for the females. In many
kinds of fish the males are much smaller than the females, and they are
believed often to be devoured by the latter, or by other fishes. The
females of some birds appear to die earlier than the males; they are also
liable to be destroyed on their nests, or whilst in charge of their young.
With insects the female larvae are often larger than those of the males,
and would consequently be more likely to be devoured. In some cases the
mature females are less active and less rapid in their movements than the
males, and could not escape so well from danger. Hence, with animals in a
state of nature, we must rely on mere estimation, in order to judge of the
proportions of the sexes at maturity; and this is but little trustworthy,
except when the inequality is strongly marked. Nevertheless, as far as a
judgment can be formed, we may conclude from the facts given in the
supplement, that the males of some few mammals, of many birds, of some fish
and insects, are considerably more numerous than the females.
The proportion between the sexes fluctuates slightly during successive
years: thus with race-horses, for every 100 mares born the stallions
varied from 107.1 in one year to 92.6 in another year, and with greyhounds
from 116.3 to 95.3. But had larger numbers been tabulated throughout an
area more extensive than England, these fluctuations would probably have
disappeared; and such as they are, would hardly suffice to lead to
effective sexual selection in a state of nature. Nevertheless, in the
cases of some few wild animals, as shewn in the supplement, the proportions
seem to fluctuate either during different seasons or in different
localities in a sufficient degree to lead to such selection. For it should
be observed that any advantage, gained during certain years or in certain
localities by those males which were able to conquer their rivals, or were
the most attractive to the females, would probably be transmitted to the
offspring, and would not subsequently be eliminated. During the succeeding
seasons, when, from the equality of the sexes, every male was able to
procure a female, the stronger or more attractive males previously produced
would still have at least as good a chance of leaving offspring as the
weaker or less attractive.
POLYGAMY.
The practice of polygamy leads to the same results as would follow from an
actual inequality in the number of the sexes; for if each male secures two
or more females, many males cannot pair; and the latter assuredly will be
the weaker or less attractive individuals. Many mammals and some few birds
are polygamous, but with animals belonging to the lower classes I have
found no evidence of this habit. The intellectual powers of such animals
are, perhaps, not sufficient to lead them to collect and guard a harem of
females. That some relation exists between polygamy and the development of
secondary sexual characters, appears nearly certain; and this supports the
view that a numerical preponderance of males would be eminently favourable
to the action of sexual selection. Nevertheless many animals, which are
strictly monogamous, especially birds, display strongly-marked secondary
sexual characters; whilst some few animals, which are polygamous, do not
have such characters.
We will first briefly run through the mammals, and then turn to birds. The
gorilla seems to be polygamous, and the male differs considerably from the
female; so it is with some baboons, which live in herds containing twice as
many adult females as males. In South America the Mycetes caraya presents
well-marked sexual differences, in colour, beard, and vocal organs; and the
male generally lives with two or three wives: the male of the Cebus
capucinus differs somewhat from the female, and appears to be polygamous.
(10. On the Gorilla, Savage and Wyman, 'Boston Journal of Natural
History,' vol. v. 1845-47, p. 423. On Cynocephalus, Brehm, 'Thierleben,'
B. i. 1864, s. 77. On Mycetes, Rengger, 'Naturgeschichte der Saugethiere
von Paraguay,' 1830, ss. 14, 20. On Cebus, Brehm, ibid. s. 108.) Little
is known on this head with respect to most other monkeys, but some species
are strictly monogamous. The ruminants are eminently polygamous, and they
present sexual differences more frequently than almost any other group of
mammals; this holds good, especially in their weapons, but also in other
characters. Most deer, cattle, and sheep are polygamous; as are most
antelopes, though some are monogamous. Sir Andrew Smith, in speaking of
the antelopes of South Africa, says that in herds of about a dozen there
was rarely more than one mature male. The Asiatic Antilope saiga appears
to be the most inordinate polygamist in the world; for Pallas (11. Pallas,
'Spicilegia Zoolog., Fasc.' xii. 1777, p. 29. Sir Andrew Smith,
'Illustrations of the Zoology of S. Africa,' 1849, pl. 29, on the Kobus.
Owen, in his 'Anatomy of Vertebrates' (vol. iii. 1868, p. 633) gives a
table shewing incidentally which species of antelopes are gregarious.)
states that the male drives away all rivals, and collects a herd of about a
hundred females and kids together; the female is hornless and has softer
hair, but does not otherwise differ much from the male. The wild horse of
the Falkland Islands and of the Western States of N. America is polygamous,
but, except in his greater size and in the proportions of his body, differs
but little from the mare. The wild boar presents well-marked sexual
characters, in his great tusks and some other points. In Europe and in
India he leads a solitary life, except during the breeding-season; but as
is believed by Sir W. Elliot, who has had many opportunities in India of
observing this animal, he consorts at this season with several females.
Whether this holds good in Europe is doubtful, but it is supported by some
evidence. The adult male Indian elephant, like the boar, passes much of
his time in solitude; but as Dr. Campbell states, when with others, "It is
rare to find more than one male with a whole herd of females"; the larger
males expelling or killing the smaller and weaker ones. The male differs
from the female in his immense tusks, greater size, strength, and
endurance; so great is the difference in these respects that the males when
caught are valued at one-fifth more than the females. (12. Dr. Campbell,
in 'Proc. Zoolog. Soc.' 1869, p. 138. See also an interesting paper by
Lieut. Johnstone, in 'Proceedings, Asiatic Society of Bengal,' May 1868.)
The sexes of other pachydermatous animals differ very little or not at all,
and, as far as known, they are not polygamists. Nor have I heard of any
species in the Orders of Cheiroptera, Edentata, Insectivora and Rodents
being polygamous, excepting that amongst the Rodents, the common rat,
according to some rat-catchers, lives with several females. Nevertheless
the two sexes of some sloths (Edentata) differ in the character and colour
of certain patches of hair on their shoulders. (13. Dr. Gray, in 'Annals
and Magazine of Natural History,' 1871, p. 302.) And many kinds of bats
(Cheiroptera) present well-marked sexual differences, chiefly in the males
possessing odoriferous glands and pouches, and by their being of a lighter
colour. (14. See Dr. Dobson's excellent paper in 'Proceedings of the
Zoological Society,' 1873, p. 241.) In the great order of Rodents, as far
as I can learn, the sexes rarely differ, and when they do so, it is but
slightly in the tint of the fur.
As I hear from Sir Andrew Smith, the lion in South Africa sometimes lives
with a single female, but generally with more, and, in one case, was found
with as many as five females; so that he is polygamous. As far as I can
discover, he is the only polygamist amongst all the terrestrial Carnivora,
and he alone presents well-marked sexual characters. If, however, we turn
to the marine Carnivora, as we shall hereafter see, the case is widely
different; for many species of seals offer extraordinary sexual
differences, and they are eminently polygamous. Thus, according to Peron,
the male sea-elephant of the Southern Ocean always possesses several
females, and the sea-lion of Forster is said to be surrounded by from
twenty to thirty females. In the North, the male sea-bear of Steller is
accompanied by even a greater number of females. It is an interesting
fact, as Dr. Gill remarks (15. 'The Eared Seals,' American Naturalist,
vol. iv. Jan. 1871.), that in the monogamous species, "or those living in
small communities, there is little difference in size between the males and
females; in the social species, or rather those of which the males have
harems, the males are vastly larger than the females."
Amongst birds, many species, the sexes of which differ greatly from each
other, are certainly monogamous. In Great Britain we see well-marked
sexual differences, for instance, in the wild-duck which pairs with a
single female, the common blackbird, and the bullfinch which is said to
pair for life. I am informed by Mr. Wallace that the like is true of the
Chatterers or Cotingidae of South America, and of many other birds. In
several groups I have not been able to discover whether the species are
polygamous or monogamous. Lesson says that birds of paradise, so
remarkable for their sexual differences, are polygamous, but Mr. Wallace
doubts whether he had sufficient evidence. Mr. Salvin tells me he has been
led to believe that humming-birds are polygamous. The male widow-bird,
remarkable for his caudal plumes, certainly seems to be a polygamist. (16.
'The Ibis,' vol. iii. 1861, p. 133, on the Progne Widow-bird. See also on
the Vidua axillaris, ibid. vol. ii. 1860, p. 211. On the polygamy of the
Capercailzie and Great Bustard, see L. Lloyd, 'Game Birds of Sweden,' 1867,
pp. 19, and 182. Montagu and Selby speak of the Black Grouse as polygamous
and of the Red Grouse as monogamous.) I have been assured by Mr. Jenner
Weir and by others, that it is somewhat common for three starlings to
frequent the same nest; but whether this is a case of polygamy or polyandry
has not been ascertained.
The Gallinaceae exhibit almost as strongly marked sexual differences as
birds of paradise or humming-birds, and many of the species are, as is well
known, polygamous; others being strictly monogamous. What a contrast is
presented between the sexes of the polygamous peacock or pheasant, and the
monogamous guinea-fowl or partridge! Many similar cases could be given, as
in the grouse tribe, in which the males of the polygamous capercailzie and
black-cock differ greatly from the females; whilst the sexes of the
monogamous red grouse and ptarmigan differ very little. In the Cursores,
except amongst the bustards, few species offer strongly-marked sexual
differences, and the great bustard (Otis tarda) is said to be polygamous.
With the Grallatores, extremely few species differ sexually, but the ruff
(Machetes pugnax) affords a marked exception, and this species is believed
by Montagu to be a polygamist. Hence it appears that amongst birds there
often exists a close relation between polygamy and the development of
strongly-marked sexual differences. I asked Mr. Bartlett, of the
Zoological Gardens, who has had very large experience with birds, whether
the male tragopan (one of the Gallinaceae) was polygamous, and I was struck
by his answering, "I do not know, but should think so from his splendid
colours."
It deserves notice that the instinct of pairing with a single female is
easily lost under domestication. The wild-duck is strictly monogamous, the
domestic-duck highly polygamous. The Rev. W.D. Fox informs me that out of
some half-tamed wild-ducks, on a large pond in his neighbourhood, so many
mallards were shot by the gamekeeper that only one was left for every seven
or eight females; yet unusually large broods were reared. The guinea-fowl
is strictly monogamous; but Mr. Fox finds that his birds succeed best when
he keeps one cock to two or three hens. Canary-birds pair in a state of
nature, but the breeders in England successfully put one male to four or
five females. I have noticed these cases, as rendering it probable that
wild monogamous species might readily become either temporarily or
permanently polygamous.
Too little is known of the habits of reptiles and fishes to enable us to
speak of their marriage arrangements. The stickle-back (Gasterosteus),
however, is said to be a polygamist (17. Noel Humphreys, 'River Gardens,'
1857.); and the male during the breeding-season differs conspicuously from
the female.
To sum up on the means through which, as far as we can judge, sexual
selection has led to the development of secondary sexual characters. It
has been shewn that the largest number of vigorous offspring will be reared
from the pairing of the strongest and best-armed males, victorious in
contests over other males, with the most vigorous and best-nourished
females, which are the first to breed in the spring. If such females
select the more attractive, and at the same time vigorous males, they will
rear a larger number of offspring than the retarded females, which must
pair with the less vigorous and less attractive males. So it will be if
the more vigorous males select the more attractive and at the same time
healthy and vigorous females; and this will especially hold good if the
male defends the female, and aids in providing food for the young. The
advantage thus gained by the more vigorous pairs in rearing a larger number
of offspring has apparently sufficed to render sexual selection efficient.
But a large numerical preponderance of males over females will be still
more efficient; whether the preponderance is only occasional and local, or
permanent; whether it occurs at birth, or afterwards from the greater
destruction of the females; or whether it indirectly follows from the
practice of polygamy.
THE MALE GENERALLY MORE MODIFIED THAN THE FEMALE.
Throughout the animal kingdom, when the sexes differ in external
appearance, it is, with rare exceptions, the male which has been the more
modified; for, generally, the female retains a closer resemblance to the
young of her own species, and to other adult members of the same group.
The cause of this seems to lie in the males of almost all animals having
stronger passions than the females. Hence it is the males that fight
together and sedulously display their charms before the females; and the
victors transmit their superiority to their male offspring. Why both sexes
do not thus acquire the characters of their fathers, will be considered
hereafter. That the males of all mammals eagerly pursue the females is
notorious to every one. So it is with birds; but many cock birds do not so
much pursue the hen, as display their plumage, perform strange antics, and
pour forth their song in her presence. The male in the few fish observed
seems much more eager than the female; and the same is true of alligators,
and apparently of Batrachians. Throughout the enormous class of insects,
as Kirby remarks, "the law is that the male shall seek the female." (18.
Kirby and Spence, 'Introduction to Entomology,' vol. iii. 1826, p. 342.)
Two good authorities, Mr. Blackwall and Mr. C. Spence Bate, tell me that
the males of spiders and crustaceans are more active and more erratic in
their habits than the females. When the organs of sense or locomotion are
present in the one sex of insects and crustaceans and absent in the other,
or when, as is frequently the case, they are more highly developed in the
one than in the other, it is, as far as I can discover, almost invariably
the male which retains such organs, or has them most developed; and this
shews that the male is the more active member in the courtship of the
sexes. (19. One parasitic Hymenopterous insect (Westwood, 'Modern Class.
of Insects,' vol. ii. p. 160) forms an exception to the rule, as the male
has rudimentary wings, and never quits the cell in which it is born, whilst
the female has well-developed wings. Audouin believes that the females of
this species are impregnated by the males which are born in the same cells
with them; but it is much more probable that the females visit other cells,
so that close inter-breeding is thus avoided. We shall hereafter meet in
various classes, with a few exceptional cases, in which the female, instead
of the male, is the seeker and wooer.)
The female, on the other hand, with the rarest exceptions, is less eager
than the male. As the illustrious Hunter (20. 'Essays and Observations,'
edited by Owen, vol. i. 1861, p. 194.) long ago observed, she generally
"requires to be courted;" she is coy, and may often be seen endeavouring
for a long time to escape from the male. Every observer of the habits of
animals will be able to call to mind instances of this kind. It is shewn
by various facts, given hereafter, and by the results fairly attributable
to sexual selection, that the female, though comparatively passive,
generally exerts some choice and accepts one male in preference to others.
Or she may accept, as appearances would sometimes lead us to believe, not
the male which is the most attractive to her, but the one which is the
least distasteful. The exertion of some choice on the part of the female
seems a law almost as general as the eagerness of the male.
We are naturally led to enquire why the male, in so many and such distinct
classes, has become more eager than the female, so that he searches for
her, and plays the more active part in courtship. It would be no advantage
and some loss of power if each sex searched for the other; but why should
the male almost always be the seeker? The ovules of plants after
fertilisation have to be nourished for a time; hence the pollen is
necessarily brought to the female organs--being placed on the stigma, by
means of insects or the wind, or by the spontaneous movements of the
stamens; and in the Algae, etc., by the locomotive power of the
antherozooids. With lowly-organised aquatic animals, permanently affixed
to the same spot and having their sexes separate, the male element is
invariably brought to the female; and of this we can see the reason, for
even if the ova were detached before fertilisation, and did not require
subsequent nourishment or protection, there would yet be greater difficulty
in transporting them than the male element, because, being larger than the
latter, they are produced in far smaller numbers. So that many of the
lower animals are, in this respect, analogous with plants. (21. Prof.
Sachs ('Lehrbuch der Botanik,' 1870, S. 633) in speaking of the male and
female reproductive cells, remarks, "verhalt sich die eine bei der
Vereinigung activ,...die andere erscheint bei der Vereinigung passiv.")
The males of affixed and aquatic animals having been led to emit their
fertilising element in this way, it is natural that any of their
descendants, which rose in the scale and became locomotive, should retain
the same habit; and they would approach the female as closely as possible,
in order not to risk the loss of the fertilising element in a long passage
of it through the water. With some few of the lower animals, the females
alone are fixed, and the males of these must be the seekers. But it is
difficult to understand why the males of species, of which the progenitors
were primordially free, should invariably have acquired the habit of
approaching the females, instead of being approached by them. But in all
cases, in order that the males should seek efficiently, it would be
necessary that they should be endowed with strong passions; and the
acquirement of such passions would naturally follow from the more eager
leaving a larger number of offspring than the less eager.
The great eagerness of the males has thus indirectly led to their much more
frequently developing secondary sexual characters than the females. But
the development of such characters would be much aided, if the males were
more liable to vary than the females--as I concluded they were--after a
long study of domesticated animals. Von Nathusius, who has had very wide
experience, is strongly of the same opinion. (22. 'Vortrage uber
Viehzucht,' 1872, p. 63.) Good evidence also in favour of this conclusion
can be produced by a comparison of the two sexes in mankind. During the
Novara Expedition (23. 'Reise der Novara: Anthropolog. Theil,' 1867, ss.
216-269. The results were calculated by Dr. Weisbach from measurements
made by Drs. K. Scherzer and Schwarz. On the greater variability of the
males of domesticated animals, see my 'Variation of Animals and Plants
under Domestication,' vol. ii. 1868, p. 75.) a vast number of measurements
was made of various parts of the body in different races, and the men were
found in almost every case to present a greater range of variation than the
women; but I shall have to recur to this subject in a future chapter. Mr.
J. Wood (24. 'Proceedings of the Royal Society,' vol. xvi. July 1868, pp.
519 and 524.), who has carefully attended to the variation of the muscles
in man, puts in italics the conclusion that "the greatest number of
abnormalities in each subject is found in the males." He had previously
remarked that "altogether in 102 subjects, the varieties of redundancy were
found to be half as many again as in females, contrasting widely with the
greater frequency of deficiency in females before described." Professor
Macalister likewise remarks (25. 'Proc. Royal Irish Academy,' vol. x.
1868, p. 123.) that variations in the muscles "are probably more common in
males than females." Certain muscles which are not normally present in
mankind are also more frequently developed in the male than in the female
sex, although exceptions to this rule are said to occur. Dr. Burt Wilder
(26. 'Massachusetts Medical Society,' vol. ii. No. 3, 1868, p. 9.) has
tabulated the cases of 152 individuals with supernumerary digits, of which
86 were males, and 39, or less than half, females, the remaining 27 being
of unknown sex. It should not, however, be overlooked that women would
more frequently endeavour to conceal a deformity of this kind than men.
Again, Dr. L. Meyer asserts that the ears of man are more variable in form
than those of a woman. (27. 'Archiv fur Path. Anat. und Phys.' 1871, p.
488.) Lastly the temperature is more variable in man than in woman. (28.
The conclusions recently arrived at by Dr. J. Stockton Hough, on the
temperature of man, are given in the 'Pop. Sci. Review,' Jan. 1st, 1874, p.
97.)
The cause of the greater general variability in the male sex, than in the
female is unknown, except in so far as secondary sexual characters are
extraordinarily variable, and are usually confined to the males; and, as we
shall presently see, this fact is, to a certain extent, intelligible.
Through the action of sexual and natural selection male animals have been
rendered in very many instances widely different from their females; but
independently of selection the two sexes, from differing constitutionally,
tend to vary in a somewhat different manner. The female has to expend much
organic matter in the formation of her ova, whereas the male expends much
force in fierce contests with his rivals, in wandering about in search of
the female, in exerting his voice, pouring out odoriferous secretions,
etc.: and this expenditure is generally concentrated within a short
period. The great vigour of the male during the season of love seems often
to intensify his colours, independently of any marked difference from the
female. (29. Prof. Mantegazza is inclined to believe ('Lettera a Carlo
Darwin,' 'Archivio per l'Anthropologia,' 1871, p. 306) that the bright
colours, common in so many male animals, are due to the presence and
retention by them of the spermatic fluid; but this can hardly be the case;
for many male birds, for instance young pheasants, become brightly coloured
in the autumn of their first year.) In mankind, and even as low down in
the organic scale as in the Lepidoptera, the temperature of the body is
higher in the male than in the female, accompanied in the case of man by a
slower pulse. (30. For mankind, see Dr. J. Stockton Hough, whose
conclusions are given in the 'Popular Science Review,' 1874, p. 97. See
Girard's observations on the Lepidoptera, as given in the 'Zoological
Record,' 1869, p. 347.) On the whole the expenditure of matter and force
by the two sexes is probably nearly equal, though effected in very
different ways and at different rates.
From the causes just specified the two sexes can hardly fail to differ
somewhat in constitution, at least during the breeding-season; and,
although they may be subjected to exactly the same conditions, they will
tend to vary in a different manner. If such variations are of no service
to either sex, they will not be accumulated and increased by sexual or
natural selection. Nevertheless, they may become permanent if the exciting
cause acts permanently; and in accordance with a frequent form of
inheritance they may be transmitted to that sex alone in which they first
appeared. In this case the two sexes will come to present permanent, yet
unimportant, differences of character. For instance, Mr. Allen shews that
with a large number of birds inhabiting the northern and southern United
States, the specimens from the south are darker-coloured than those from
the north; and this seems to be the direct result of the difference in
temperature, light, etc., between the two regions. Now, in some few cases,
the two sexes of the same species appear to have been differently affected;
in the Agelaeus phoeniceus the males have had their colours greatly
intensified in the south; whereas with Cardinalis virginianus it is the
females which have been thus affected; with Quiscalus major the females
have been rendered extremely variable in tint, whilst the males remain
nearly uniform. (31. 'Mammals and Birds of E. Florida,' pp. 234, 280,
295.)
A few exceptional cases occur in various classes of animals, in which the
females instead of the males have acquired well pronounced secondary sexual
characters, such as brighter colours, greater size, strength, or pugnacity.
With birds there has sometimes been a complete transposition of the
ordinary characters proper to each sex; the females having become the more
eager in courtship, the males remaining comparatively passive, but
apparently selecting the more attractive females, as we may infer from the
results. Certain hen birds have thus been rendered more highly coloured or
otherwise ornamented, as well as more powerful and pugnacious than the
cocks; these characters being transmitted to the female offspring alone.
It may be suggested that in some cases a double process of selection has
been carried on; that the males have selected the more attractive females,
and the latter the more attractive males. This process, however, though it
might lead to the modification of both sexes, would not make the one sex
different from the other, unless indeed their tastes for the beautiful
differed; but this is a supposition too improbable to be worth considering
in the case of any animal, excepting man. There are, however, many animals
in which the sexes resemble each other, both being furnished with the same
ornaments, which analogy would lead us to attribute to the agency of sexual
selection. In such cases it may be suggested with more plausibility, that
there has been a double or mutual process of sexual selection; the more
vigorous and precocious females selecting the more attractive and vigorous
males, the latter rejecting all except the more attractive females. But
from what we know of the habits of animals, this view is hardly probable,
for the male is generally eager to pair with any female. It is more
probable that the ornaments common to both sexes were acquired by one sex,
generally the male, and then transmitted to the offspring of both sexes.
If, indeed, during a lengthened period the males of any species were
greatly to exceed the females in number, and then during another lengthened
period, but under different conditions, the reverse were to occur, a
double, but not simultaneous, process of sexual selection might easily be
carried on, by which the two sexes might be rendered widely different.
We shall hereafter see that many animals exist, of which neither sex is
brilliantly coloured or provided with special ornaments, and yet the
members of both sexes or of one alone have probably acquired simple
colours, such as white or black, through sexual selection. The absence of
bright tints or other ornaments may be the result of variations of the
right kind never having occurred, or of the animals themselves having
preferred plain black or white. Obscure tints have often been developed
through natural selection for the sake of protection, and the acquirement
through sexual selection of conspicuous colours, appears to have been
sometimes checked from the danger thus incurred. But in other cases the
males during long ages may have struggled together for the possession of
the females, and yet no effect will have been produced, unless a larger
number of offspring were left by the more successful males to inherit their
superiority, than by the less successful: and this, as previously shewn,
depends on many complex contingencies.
Sexual selection acts in a less rigorous manner than natural selection.
The latter produces its effects by the life or death at all ages of the
more or less successful individuals. Death, indeed, not rarely ensues from
the conflicts of rival males. But generally the less successful male
merely fails to obtain a female, or obtains a retarded and less vigorous
female later in the season, or, if polygamous, obtains fewer females; so
that they leave fewer, less vigorous, or no offspring. In regard to
structures acquired through ordinary or natural selection, there is in most
cases, as long as the conditions of life remain the same, a limit to the
amount of advantageous modification in relation to certain special
purposes; but in regard to structures adapted to make one male victorious
over another, either in fighting or in charming the female, there is no
definite limit to the amount of advantageous modification; so that as long
as the proper variations arise the work of sexual selection will go on.
This circumstance may partly account for the frequent and extraordinary
amount of variability presented by secondary sexual characters.
Nevertheless, natural selection will determine that such characters shall
not be acquired by the victorious males, if they would be highly injurious,
either by expending too much of their vital powers, or by exposing them to
any great danger. The development, however, of certain structures--of the
horns, for instance, in certain stags--has been carried to a wonderful
extreme; and in some cases to an extreme which, as far as the general
conditions of life are concerned, must be slightly injurious to the male.
From this fact we learn that the advantages which favoured males derive
from conquering other males in battle or courtship, and thus leaving a
numerous progeny, are in the long run greater than those derived from
rather more perfect adaptation to their conditions of life. We shall
further see, and it could never have been anticipated, that the power to
charm the female has sometimes been more important than the power to
conquer other males in battle.
LAWS OF INHERITANCE.
In order to understand how sexual selection has acted on many animals of
many classes, and in the course of ages has produced a conspicuous result,
it is necessary to bear in mind the laws of inheritance, as far as they are
known. Two distinct elements are included under the term "inheritance"--
the transmission, and the development of characters; but as these generally
go together, the distinction is often overlooked. We see this distinction
in those characters which are transmitted through the early years of life,
but are developed only at maturity or during old age. We see the same
distinction more clearly with secondary sexual characters, for these are
transmitted through both sexes, though developed in one alone. That they
are present in both sexes, is manifest when two species, having strongly-
marked sexual characters, are crossed, for each transmits the characters
proper to its own male and female sex to the hybrid offspring of either
sex. The same fact is likewise manifest, when characters proper to the
male are occasionally developed in the female when she grows old or becomes
diseased, as, for instance, when the common hen assumes the flowing tail-
feathers, hackles, comb, spurs, voice, and even pugnacity of the cock.
Conversely, the same thing is evident, more or less plainly, with castrated
males. Again, independently of old age or disease, characters are
occasionally transferred from the male to the female, as when, in certain
breeds of the fowl, spurs regularly appear in the young and healthy
females. But in truth they are simply developed in the female; for in
every breed each detail in the structure of the spur is transmitted through
the female to her male offspring. Many cases will hereafter be given,
where the female exhibits, more or less perfectly, characters proper to the
male, in whom they must have been first developed, and then transferred to
the female. The converse case of the first development of characters in
the female and of transference to the male, is less frequent; it will
therefore be well to give one striking instance. With bees the pollen-
collecting apparatus is used by the female alone for gathering pollen for
the larvae, yet in most of the species it is partially developed in the
males to whom it is quite useless, and it is perfectly developed in the
males of Bombus or the humble-bee. (32. H. Muller, 'Anwendung der
Darwin'schen Lehre,' etc., Verh. d. n. V. Jahrg., xxix. p. 42.) As not a
single other Hymenopterous insect, not even the wasp, which is closely
allied to the bee, is provided with a pollen-collecting apparatus, we have
no grounds for supposing that male bees primordially collected pollen as
well as the females; although we have some reason to suspect that male
mammals primordially suckled their young as well as the females. Lastly,
in all cases of reversion, characters are transmitted through two, three,
or many more generations, and are then developed under certain unknown
favourable conditions. This important distinction between transmission and
development will be best kept in mind by the aid of the hypothesis of
pangenesis. According to this hypothesis, every unit or cell of the body
throws off gemmules or undeveloped atoms, which are transmitted to the
offspring of both sexes, and are multiplied by self-division. They may
remain undeveloped during the early years of life or during successive
generations; and their development into units or cells, like those from
which they were derived, depends on their affinity for, and union with
other units or cells previously developed in the due order of growth.
INHERITANCE AT CORRESPONDING PERIODS OF LIFE.
This tendency is well established. A new character, appearing in a young
animal, whether it lasts throughout life or is only transient, will, in
general, reappear in the offspring at the same age and last for the same
time. If, on the other hand, a new character appears at maturity, or even
during old age, it tends to reappear in the offspring at the same advanced
age. When deviations from this rule occur, the transmitted characters much
oftener appear before, than after the corresponding age. As I have dwelt
on this subject sufficiently in another work (33. The 'Variation of
Animals and Plants under Domestication,' vol. ii. 1868, p. 75. In the last
chapter but one, the provisional hypothesis of pangenesis, above alluded
to, is fully explained.), I will here merely give two or three instances,
for the sake of recalling the subject to the reader's mind. In several
breeds of the Fowl, the down-covered chickens, the young birds in their
first true plumage, and the adults differ greatly from one another, as well
as from their common parent-form, the Gallus bankiva; and these characters
are faithfully transmitted by each breed to their offspring at the
corresponding periods of life. For instance, the chickens of spangled
Hamburgs, whilst covered with down, have a few dark spots on the head and
rump, but are not striped longitudinally, as in many other breeds; in their
first true plumage, "they are beautifully pencilled," that is each feather
is transversely marked by numerous dark bars; but in their second plumage
the feathers all become spangled or tipped with a dark round spot. (34.
These facts are given on the high authority of a great breeder, Mr. Teebay;
see Tegetmeier's 'Poultry Book,' 1868, p. 158. On the characters of
chickens of different breeds, and on the breeds of the pigeon, alluded to
in the following paragraph, see 'Variation of Animals,' etc., vol. i. pp.
160, 249; vol. ii. p. 77.) Hence in this breed variations have occurred
at, and been transmitted to, three distinct periods of life. The Pigeon
offers a more remarkable case, because the aboriginal parent species does
not undergo any change of plumage with advancing age, excepting that at
maturity the breast becomes more iridescent; yet there are breeds which do
not acquire their characteristic colours until they have moulted two,
three, or four times; and these modifications of plumage are regularly
transmitted.
INHERITANCE AT CORRESPONDING SEASONS OF THE YEAR.
With animals in a state of nature, innumerable instances occur of
characters appearing periodically at different seasons. We see this in the
horns of the stag, and in the fur of Artic animals which becomes thick and
white during the winter. Many birds acquire bright colours and other
decorations during the breeding-season alone. Pallas states (35. 'Novae
species Quadrupedum e Glirium ordine,' 1778, p. 7. On the transmission of
colour by the horse, see 'Variation of Animals and Plants under
Domestication,' vol. i. p. 51. Also vol. ii. p. 71, for a general
discussion on 'Inheritance as limited by Sex.'), that in Siberia domestic
cattle and horses become lighter-coloured during the winter; and I have
myself observed, and heard of similar strongly marked changes of colour,
that is, from brownish cream-colour or reddish-brown to a perfect white, in
several ponies in England. Although I do not know that this tendency to
change the colour of the coat during different seasons is transmitted, yet
it probably is so, as all shades of colour are strongly inherited by the
horse. Nor is this form of inheritance, as limited by the seasons, more
remarkable than its limitation by age or sex.
INHERITANCE AS LIMITED BY SEX.
The equal transmission of characters to both sexes is the commonest form of
inheritance, at least with those animals which do not present strongly-
marked sexual differences, and indeed with many of these. But characters
are somewhat commonly transferred exclusively to that sex, in which they
first appear. Ample evidence on this head has been advanced in my work on
'Variation under Domestication,' but a few instances may here be given.
There are breeds of the sheep and goat, in which the horns of the male
differ greatly in shape from those of the female; and these differences,
acquired under domestication, are regularly transmitted to the same sex.
As a rule, it is the females alone in cats which are tortoise-shell, the
corresponding colour in the males being rusty-red. With most breeds of the
fowl, the characters proper to each sex are transmitted to the same sex
alone. So general is this form of transmission that it is an anomaly when
variations in certain breeds are transmitted equally to both sexes. There
are also certain sub-breeds of the fowl in which the males can hardly be
distinguished from one another, whilst the females differ considerably in
colour. The sexes of the pigeon in the parent-species do not differ in any
external character; nevertheless, in certain domesticated breeds the male
is coloured differently from the female. (36. Dr. Chapuis, 'Le Pigeon
Voyageur Belge,' 1865, p. 87. Boitard et Corbie, 'Les Pigeons de Voliere,'
etc., 1824, p. 173. See, also, on similar differences in certain breeds at
Modena, 'Le variazioni dei Colombi domestici,' del Paolo Bonizzi, 1873.)
The wattle in the English Carrier pigeon, and the crop in the Pouter, are
more highly developed in the male than in the female; and although these
characters have been gained through long-continued selection by man, the
slight differences between the sexes are wholly due to the form of
inheritance which has prevailed; for they have arisen, not from, but rather
in opposition to, the wish of the breeder.
Most of our domestic races have been formed by the accumulation of many
slight variations; and as some of the successive steps have been
transmitted to one sex alone, and some to both sexes, we find in the
different breeds of the same species all gradations between great sexual
dissimilarity and complete similarity. Instances have already been given
with the breeds of the fowl and pigeon, and under nature analogous cases
are common. With animals under domestication, but whether in nature I will
not venture to say, one sex may lose characters proper to it, and may thus
come somewhat to resemble the opposite sex; for instance, the males of some
breeds of the fowl have lost their masculine tail-plumes and hackles. On
the other hand, the differences between the sexes may be increased under
domestication, as with merino sheep, in which the ewes have lost their
horns. Again, characters proper to one sex may suddenly appear in the
other sex; as in those sub-breeds of the fowl in which the hens acquire
spurs whilst young; or, as in certain Polish sub-breeds, in which the
females, as there is reason to believe, originally acquired a crest, and
subsequently transferred it to the males. All these cases are intelligible
on the hypothesis of pangenesis; for they depend on the gemmules of certain
parts, although present in both sexes, becoming, through the influence of
domestication, either dormant or developed in either sex.
There is one difficult question which it will be convenient to defer to a
future chapter; namely, whether a character at first developed in both
sexes, could through selection be limited in its development to one sex
alone. If, for instance, a breeder observed that some of his pigeons (of
which the characters are usually transferred in an equal degree to both
sexes) varied into pale blue, could he by long-continued selection make a
breed, in which the males alone should be of this tint, whilst the females
remained unchanged? I will here only say, that this, though perhaps not
impossible, would be extremely difficult; for the natural result of
breeding from the pale-blue males would be to change the whole stock of
both sexes to this tint. If, however, variations of the desired tint
appeared, which were from the first limited in their development to the
male sex, there would not be the least difficulty in making a breed with
the two sexes of a different colour, as indeed has been effected with a
Belgian breed, in which the males alone are streaked with black. In a
similar manner, if any variation appeared in a female pigeon, which was
from the first sexually limited in its development to the females, it would
be easy to make a breed with the females alone thus characterised; but if
the variation was not thus originally limited, the process would be
extremely difficult, perhaps impossible. (37. Since the publication of
the first edition of this work, it has been highly satisfactory to me to
find the following remarks (the 'Field,' Sept. 1872) from so experienced a
breeder as Mr. Tegetmeier. After describing some curious cases in pigeons,
of the transmission of colour by one sex alone, and the formation of a sub-
breed with this character, he says: "It is a singular circumstance that
Mr. Darwin should have suggested the possibility of modifying the sexual
colours of birds by a course of artificial selection. When he did so, he
was in ignorance of these facts that I have related; but it is remarkable
how very closely he suggested the right method of procedure.")
ON THE RELATION BETWEEN THE PERIOD OF DEVELOPMENT OF A CHARACTER AND ITS
TRANSMISSION TO ONE SEX OR TO BOTH SEXES.
Why certain characters should be inherited by both sexes, and other
characters by one sex alone, namely by that sex in which the character
first appeared, is in most cases quite unknown. We cannot even conjecture
why with certain sub-breeds of the pigeon, black striae, though transmitted
through the female, should be developed in the male alone, whilst every
other character is equally transferred to both sexes. Why, again, with
cats, the tortoise-shell colour should, with rare exceptions, be developed
in the female alone. The very same character, such as deficient or
supernumerary digits, colour-blindness, etc., may with mankind be inherited
by the males alone of one family, and in another family by the females
alone, though in both cases transmitted through the opposite as well as
through the same sex. (38. References are given in my 'Variation of
Animals and Plants under Domestication,' vol. ii. p. 72.) Although we are
thus ignorant, the two following rules seem often to hold good--that
variations which first appear in either sex at a late period of life, tend
to be developed in the same sex alone; whilst variations which first appear
early in life in either sex tend to be developed in both sexes. I am,
however, far from supposing that this is the sole determining cause. As I
have not elsewhere discussed this subject, and it has an important bearing
on sexual selection, I must here enter into lengthy and somewhat intricate
details.
It is in itself probable that any character appearing at an early age would
tend to be inherited equally by both sexes, for the sexes do not differ
much in constitution before the power of reproduction is gained. On the
other hand, after this power has been gained and the sexes have come to
differ in constitution, the gemmules (if I may again use the language of
pangenesis) which are cast off from each varying part in the one sex would
be much more likely to possess the proper affinities for uniting with the
tissues of the same sex, and thus becoming developed, than with those of
the opposite sex.
I was first led to infer that a relation of this kind exists, from the fact
that whenever and in whatever manner the adult male differs from the adult
female, he differs in the same manner from the young of both sexes. The
generality of this fact is quite remarkable: it holds good with almost all
mammals, birds, amphibians, and fishes; also with many crustaceans,
spiders, and some few insects, such as certain orthoptera and libellulae.
In all these cases the variations, through the accumulation of which the
male acquired his proper masculine characters, must have occurred at a
somewhat late period of life; otherwise the young males would have been
similarly characterised; and conformably with our rule, the variations are
transmitted to and developed in the adult males alone. When, on the other
hand, the adult male closely resembles the young of both sexes (these, with
rare exceptions, being alike), he generally resembles the adult female; and
in most of these cases the variations through which the young and old
acquired their present characters, probably occurred, according to our
rule, during youth. But there is here room for doubt, for characters are
sometimes transferred to the offspring at an earlier age than that at which
they first appeared in the parents, so that the parents may have varied
when adult, and have transferred their characters to their offspring whilst
young. There are, moreover, many animals, in which the two sexes closely
resemble each other, and yet both differ from their young: and here the
characters of the adults must have been acquired late in life;
nevertheless, these characters, in apparent contradiction to our rule, are
transferred to both sexes. We must not however, overlook the possibility
or even probability of successive variations of the same nature occurring,
under exposure to similar conditions, simultaneously in both sexes at a
rather late period of life; and in this case the variations would be
transferred to the offspring of both sexes at a corresponding late age; and
there would then be no real contradiction to the rule that variations
occurring late in life are transferred exclusively to the sex in which they
first appeared. This latter rule seems to hold true more generally than
the second one, namely, that variations which occur in either sex early in
life tend to be transferred to both sexes. As it was obviously impossible
even to estimate in how large a number of cases throughout the animal
kingdom these two propositions held good, it occurred to me to investigate
some striking or crucial instances, and to rely on the result.
An excellent case for investigation is afforded by the Deer family. In all
the species, but one, the horns are developed only in the males, though
certainly transmitted through the females, and capable of abnormal
development in them. In the reindeer, on the other hand, the female is
provided with horns; so that in this species, the horns ought, according to
our rule, to appear early in life, long before the two sexes are mature and
have come to differ much in constitution. In all the other species the
horns ought to appear later in life, which would lead to their development
in that sex alone, in which they first appeared in the progenitor of the
whole Family. Now in seven species, belonging to distinct sections of the
family and inhabiting different regions, in which the stags alone bear
horns, I find that the horns first appear at periods, varying from nine
months after birth in the roebuck, to ten, twelve or even more months in
the stags of the six other and larger species. (39. I am much obliged to
Mr. Cupples for having made enquiries for me in regard to the Roebuck and
Red Deer of Scotland from Mr. Robertson, the experienced head-forester to
the Marquis of Breadalbane. In regard to Fallow-deer, I have to thank Mr.
Eyton and others for information. For the Cervus alces of N. America, see
'Land and Water,' 1868, pp. 221 and 254; and for the C. Virginianus and
strongyloceros of the same continent, see J.D. Caton, in 'Ottawa Acad. of
Nat. Sc.' 1868, p. 13. For Cervus Eldi of Pegu, see Lieut. Beaven,
'Proccedings of the Zoological Society,' 1867, p. 762.) But with the
reindeer the case is widely different; for, as I hear from Prof. Nilsson,
who kindly made special enquiries for me in Lapland, the horns appear in
the young animals within four or five weeks after birth, and at the same
time in both sexes. So that here we have a structure, developed at a most
unusually early age in one species of the family, and likewise common to
both sexes in this one species alone.
In several kinds of antelopes, only the males are provided with horns,
whilst in the greater number both sexes bear horns. With respect to the
period of development, Mr. Blyth informs me that there was at one time in
the Zoological Gardens a young koodoo (Ant. strepsiceros), of which the
males alone are horned, and also the young of a closely-allied species, the
eland (Ant. oreas), in which both sexes are horned. Now it is in strict
conformity with our rule, that in the young male koodoo, although ten
months old, the horns were remarkably small, considering the size
ultimately attained by them; whilst in the young male eland, although only
three months old, the horns were already very much larger than in the
koodoo. It is also a noticeable fact that in the prong-horned antelope
(40. Antilocapra Americana. I have to thank Dr. Canfield for information
with respect to the horns of the female: see also his paper in
'Proceedings of the Zoological Society,' 1866, p. 109. Also Owen, 'Anatomy
of Vertebrates,' vol. iii. p. 627), only a few of the females, about one in
five, have horns, and these are in a rudimentary state, though sometimes
above four inches long: so that as far as concerns the possession of horns
by the males alone, this species is in an intermediate condition, and the
horns do not appear until about five or six months after birth. Therefore
in comparison with what little we know of the development of the horns in
other antelopes, and from what we do know with respect to the horns of
deer, cattle, etc., those of the prong-horned antelope appear at an
intermediate period of life,--that is, not very early, as in cattle and
sheep, nor very late, as in the larger deer and antelopes. The horns of
sheep, goats, and cattle, which are well developed in both sexes, though
not quite equal in size, can be felt, or even seen, at birth or soon
afterwards. (41. I have been assured that the horns of the sheep in North
Wales can always be felt, and are sometimes even an inch in length, at
birth. Youatt says ('Cattle,' 1834, p. 277), that the prominence of the
frontal bone in cattle penetrates the cutis at birth, and that the horny
matter is soon formed over it.) Our rule, however, seems to fail in some
breeds of sheep, for instance merinos, in which the rams alone are horned;
for I cannot find on enquiry (42. I am greatly indebted to Prof. Victor
Carus for having made enquiries for me, from the highest authorities, with
respect to the merino sheep of Saxony. On the Guinea coast of Africa there
is, however, a breed of sheep in which, as with merinos, the rams alone
bear horns; and Mr. Winwood Reade informs me that in one case observed by
him, a young ram, born on Feb. 10th, first shewed horns on March 6th, so
that in this instance, in conformity with rule, the development of the
horns occurred at a later period of life than in Welsh sheep, in which both
sexes are horned.), that the horns are developed later in life in this
breed than in ordinary sheep in which both sexes are horned. But with
domesticated sheep the presence or absence of horns is not a firmly fixed
character; for a certain proportion of the merino ewes bear small horns,
and some of the rams are hornless; and in most breeds hornless ewes are
occasionally produced.
Dr. W. Marshall has lately made a special study of the protuberances so
common on the heads of birds (43. 'Uber die knochernen Schadelhocker der
Vogel,' in the 'Niederland. Archiv fur Zoologie,' B.i. Heft 2, 1872.), and
he comes to the following conclusion:--that with those species in which
they are confined to the males, they are developed late in life; whereas
with those species in which they are common to the two sexes, they are
developed at a very early period. This is certainly a striking
confirmation of my two laws of inheritance.
In most of the species of the splendid family of the Pheasants, the males
differ conspicuously from the females, and they acquire their ornaments at
a rather late period of life. The eared pheasant (Crossoptilon auritum),
however, offers a remarkable exception, for both sexes possess the fine
caudal plumes, the large ear-tufts and the crimson velvet about the head; I
find that all these characters appear very early in life in accordance with
rule. The adult male can, however, be distinguished from the adult female
by the presence of spurs; and conformably with our rule, these do not begin
to be developed before the age of six months, as I am assured by Mr.
Bartlett, and even at this age, the two sexes can hardly be distinguished.
(44. In the common peacock (Pavo cristatus) the male alone possesses
spurs, whilst both sexes of the Java Peacock (P. muticus) offer the unusual
case of being furnished with spurs. Hence I fully expected that in the
latter species they would have been developed earlier in life than in the
common peacock; but M. Hegt of Amsterdam informs me, that with young birds
of the previous year, of both species, compared on April 23rd, 1869, there
was no difference in the development of the spurs. The spurs, however,
were as yet represented merely by slight knobs or elevations. I presume
that I should have been informed if any difference in the rate of
development had been observed subsequently.) The male and female Peacock
differ conspicuously from each other in almost every part of their plumage,
except in the elegant head-crest, which is common to both sexes; and this
is developed very early in life, long before the other ornaments, which are
confined to the male. The wild-duck offers an analogous case, for the
beautiful green speculum on the wings is common to both sexes, though
duller and somewhat smaller in the female, and it is developed early in
life, whilst the curled tail-feathers and other ornaments of the male are
developed later. (45. In some other species of the Duck family the
speculum differs in a greater degree in the two sexes; but I have not been
able to discover whether its full development occurs later in life in the
males of such species, than in the male of the common duck, as ought to be
the case according to our rule. With the allied Mergus cucullatus we have,
however, a case of this kind: the two sexes differ conspicuously in
general plumage, and to a considerable degree in the speculum, which is
pure white in the male and greyish-white in the female. Now the young
males at first entirely resemble the females, and have a greyish-white
speculum, which becomes pure white at an earlier age than that at which the
adult male acquires his other and more strongly-marked sexual differences:
see Audubon, 'Ornithological Biography,' vol. iii. 1835, pp. 249-250.)
Between such extreme cases of close sexual resemblance and wide
dissimilarity, as those of the Crossoptilon and peacock, many intermediate
ones could be given, in which the characters follow our two rules in their
order of development.
As most insects emerge from the pupal state in a mature condition, it is
doubtful whether the period of development can determine the transference
of their characters to one or to both sexes. But we do not know that the
coloured scales, for instance, in two species of butterflies, in one of
which the sexes differ in colour, whilst in the other they are alike, are
developed at the same relative age in the cocoon. Nor do we know whether
all the scales are simultaneously developed on the wings of the same
species of butterfly, in which certain coloured marks are confined to one
sex, whilst others are common to both sexes. A difference of this kind in
the period of development is not so improbable as it may at first appear;
for with the Orthoptera, which assume their adult state, not by a single
metamorphosis, but by a succession of moults, the young males of some
species at first resemble the females, and acquire their distinctive
masculine characters only at a later moult. Strictly analogous cases occur
at the successive moults of certain male crustaceans.
We have as yet considered the transference of characters, relatively to
their period of development, only in species in a natural state; we will
now turn to domesticated animals, and first touch on monstrosities and
diseases. The presence of supernumerary digits, and the absence of certain
phalanges, must be determined at an early embryonic period--the tendency to
profuse bleeding is at least congenital, as is probably colour-blindness--
yet these peculiarities, and other similar ones, are often limited in their
transmission to one sex; so that the rule that characters, developed at an
early period, tend to be transmitted to both sexes, here wholly fails. But
this rule, as before remarked, does not appear to be nearly so general as
the converse one, namely, that characters which appear late in life in one
sex are transmitted exclusively to the same sex. From the fact of the
above abnormal peculiarities becoming attached to one sex, long before the
sexual functions are active, we may infer that there must be some
difference between the sexes at an extremely early age. With respect to
sexually-limited diseases, we know too little of the period at which they
originate, to draw any safe conclusion. Gout, however, seems to fall under
our rule, for it is generally caused by intemperance during manhood, and is
transmitted from the father to his sons in a much more marked manner than
to his daughters.
In the various domestic breeds of sheep, goats, and cattle, the males
differ from their respective females in the shape or development of their
horns, forehead, mane, dewlap, tail, and hump on the shoulders; and these
peculiarities, in accordance with our rule, are not fully developed until a
rather late period of life. The sexes of dogs do not differ, except that
in certain breeds, especially in the Scotch deer-hound, the male is much
larger and heavier than the female; and, as we shall see in a future
chapter, the male goes on increasing in size to an unusually late period of
life, which, according to rule, will account for his increased size being
transmitted to his male offspring alone. On the other hand, the tortoise-
shell colour, which is confined to female cats, is quite distinct at birth,
and this case violates the rule. There is a breed of pigeons in which the
males alone are streaked with black, and the streaks can be detected even
in the nestlings; but they become more conspicuous at each successive
moult, so that this case partly opposes and partly supports the rule. With
the English Carrier and Pouter pigeons, the full development of the wattle
and the crop occurs rather late in life, and conformably with the rule,
these characters are transmitted in full perfection to the males alone.
The following cases perhaps come within the class previously alluded to, in
which both sexes have varied in the same manner at a rather late period of
life, and have consequently transferred their new characters to both sexes
at a corresponding late period; and if so, these cases are not opposed to
our rule:--there exist sub-breeds of the pigeon, described by Neumeister
(46. 'Das Ganze der Taubenzucht,' 1837, ss. 21, 24. For the case of the
streaked pigeons, see Dr. Chapuis, 'Le pigeon voyageur Belge,' 1865, p.
87.), in which both sexes change their colour during two or three moults
(as is likewise the case with the Almond Tumbler); nevertheless, these
changes, though occurring rather late in life, are common to both sexes.
One variety of the Canary-bird, namely the London Prize, offers a nearly
analogous case.
With the breeds of the Fowl the inheritance of various characters by one or
both sexes, seems generally determined by the period at which such
characters are developed. Thus in all the many breeds in which the adult
male differs greatly in colour from the female, as well as from the wild
parent-species, he differs also from the young male, so that the newly-
acquired characters must have appeared at a rather late period of life. On
the other hand, in most of the breeds in which the two sexes resemble each
other, the young are coloured in nearly the same manner as their parents,
and this renders it probable that their colours first appeared early in
life. We have instances of this fact in all black and white breeds, in
which the young and old of both sexes are alike; nor can it be maintained
that there is something peculiar in a black or white plumage, which leads
to its transference to both sexes; for the males alone of many natural
species are either black or white, the females being differently coloured.
With the so-called Cuckoo sub-breeds of the fowl, in which the feathers are
transversely pencilled with dark stripes, both sexes and the chickens are
coloured in nearly the same manner. The laced plumage of the Sebright
bantam is the same in both sexes, and in the young chickens the wing-
feathers are distinctly, though imperfectly laced. Spangled Hamburgs,
however, offer a partial exception; for the two sexes, though not quite
alike, resemble each other more closely than do the sexes of the aboriginal
parent-species; yet they acquire their characteristic plumage late in life,
for the chickens are distinctly pencilled. With respect to other
characters besides colour, in the wild-parent species and in most of the
domestic breeds, the males alone possess a well-developed comb; but in the
young of the Spanish fowl it is largely developed at a very early age, and,
in accordance with this early development in the male, it is of unusual
size in the adult female. In the Game breeds pugnacity is developed at a
wonderfully early age, of which curious proofs could be given; and this
character is transmitted to both sexes, so that the hens, from their
extreme pugnacity, are now generally exhibited in separate pens. With the
Polish breeds the bony protuberance of the skull which supports the crest
is partially developed even before the chickens are hatched, and the crest
itself soon begins to grow, though at first feebly (47. For full
particulars and references on all these points respecting the several
breeds of the Fowl, see 'Variation of Animals and Plants under
Domestication,' vol. i. pp. 250, 256. In regard to the higher animals, the
sexual differences which have arisen under domestication are described in
the same work under the head of each species.); and in this breed the
adults of both sexes are characterised by a great bony protuberance and an
immense crest.
Finally, from what we have now seen of the relation which exists in many
natural species and domesticated races, between the period of the
development of their characters and the manner of their transmission--for
example, the striking fact of the early growth of the horns in the
reindeer, in which both sexes bear horns, in comparison with their much
later growth in the other species in which the male alone bears horns--we
may conclude that one, though not the sole cause of characters being
exclusively inherited by one sex, is their development at a late age. And
secondly, that one, though apparently a less efficient cause of characters
being inherited by both sexes, is their development at an early age, whilst
the sexes differ but little in constitution. It appears, however, that
some difference must exist between the sexes even during a very early
embryonic period, for characters developed at this age not rarely become
attached to one sex.
SUMMARY AND CONCLUDING REMARKS.
From the foregoing discussion on the various laws of inheritance, we learn
that the characters of the parents often, or even generally, tend to become
developed in the offspring of the same sex, at the same age, and
periodically at the same season of the year, in which they first appeared
in the parents. But these rules, owing to unknown causes, are far from
being fixed. Hence during the modification of a species, the successive
changes may readily be transmitted in different ways; some to one sex, and
some to both; some to the offspring at one age, and some to the offspring
at all ages. Not only are the laws of inheritance extremely complex, but
so are the causes which induce and govern variability. The variations thus
induced are preserved and accumulated by sexual selection, which is in
itself an extremely complex affair, depending, as it does, on the ardour in
love, the courage, and the rivalry of the males, as well as on the powers
of perception, the taste, and will of the female. Sexual selection will
also be largely dominated by natural selection tending towards the general
welfare of the species. Hence the manner in which the individuals of
either or both sexes have been affected through sexual selection cannot
fail to be complex in the highest degree.
When variations occur late in life in one sex, and are transmitted to the
same sex at the same age, the other sex and the young are left unmodified.
When they occur late in life, but are transmitted to both sexes at the same
age, the young alone are left unmodified. Variations, however, may occur
at any period of life in one sex or in both, and be transmitted to both
sexes at all ages, and then all the individuals of the species are
similarly modified. In the following chapters it will be seen that all
these cases frequently occur in nature.
Sexual selection can never act on any animal before the age for
reproduction arrives. From the great eagerness of the male it has
generally acted on this sex and not on the females. The males have thus
become provided with weapons for fighting with their rivals, with organs
for discovering and securely holding the female, and for exciting or
charming her. When the sexes differ in these respects, it is also, as we
have seen, an extremely general law that the adult male differs more or
less from the young male; and we may conclude from this fact that the
successive variations, by which the adult male became modified, did not
generally occur much before the age for reproduction. Whenever some or
many of the variations occurred early in life, the young males would
partake more or less of the characters of the adult males; and differences
of this kind between the old and young males may be observed in many
species of animals.
It is probable that young male animals have often tended to vary in a
manner which would not only have been of no use to them at an early age,
but would have been actually injurious--as by acquiring bright colours,
which would render them conspicuous to their enemies, or by acquiring
structures, such as great horns, which would expend much vital force in
their development. Variations of this kind occurring in the young males
would almost certainly be eliminated through natural selection. With the
adult and experienced males, on the other hand, the advantages derived from
the acquisition of such characters, would more than counterbalance some
exposure to danger, and some loss of vital force.
As variations which give to the male a better chance of conquering other
males, or of finding, securing, or charming the opposite sex, would, if
they happened to arise in the female, be of no service to her, they would
not be preserved in her through sexual selection. We have also good
evidence with domesticated animals, that variations of all kinds are, if
not carefully selected, soon lost through intercrossing and accidental
deaths. Consequently in a state of nature, if variations of the above kind
chanced to arise in the female line, and to be transmitted exclusively in
this line, they would be extremely liable to be lost. If, however, the
females varied and transmitted their newly acquired characters to their
offspring of both sexes, the characters which were advantageous to the
males would be preserved by them through sexual selection, and the two
sexes would in consequence be modified in the same manner, although such
characters were of no use to the females: but I shall hereafter have to
recur to these more intricate contingencies. Lastly, the females may
acquire, and apparently have often acquired by transference, characters
from the male sex.
As variations occurring later in life, and transmitted to one sex alone,
have incessantly been taken advantage of and accumulated through sexual
selection in relation to the reproduction of the species; therefore it
appears, at first sight, an unaccountable fact that similar variations have
not frequently been accumulated through natural selection, in relation to
the ordinary habits of life. If this had occurred, the two sexes would
often have been differently modified, for the sake, for instance, of
capturing prey or of escaping from danger. Differences of this kind
between the two sexes do occasionally occur, especially in the lower
classes. But this implies that the two sexes follow different habits in
their struggles for existence, which is a rare circumstance with the higher
animals. The case, however, is widely different with the reproductive
functions, in which respect the sexes necessarily differ. For variations
in structure which are related to these functions, have often proved of
value to one sex, and from having arisen at a late period of life, have
been transmitted to one sex alone; and such variations, thus preserved and
transmitted, have given rise to secondary sexual characters.
In the following chapters, I shall treat of the secondary sexual characters
in animals of all classes, and shall endeavour in each case to apply the
principles explained in the present chapter. The lowest classes will
detain us for a very short time, but the higher animals, especially birds,
must be treated at considerable length. It should be borne in mind that
for reasons already assigned, I intend to give only a few illustrative
instances of the innumerable structures by the aid of which the male finds
the female, or, when found, holds her. On the other hand, all structures
and instincts by the aid of which the male conquers other males, and by
which he allures or excites the female, will be fully discussed, as these
are in many ways the most interesting.
SUPPLEMENT ON THE PROPORTIONAL NUMBERS OF THE TWO SEXES IN ANIMALS
BELONGING TO VARIOUS CLASSES.
As no one, as far as I can discover, has paid attention to the relative
numbers of the two sexes throughout the animal kingdom, I will here give
such materials as I have been able to collect, although they are extremely
imperfect. They consist in only a few instances of actual enumeration, and
the numbers are not very large. As the proportions are known with
certainty only in mankind, I will first give them as a standard of
comparison.
MAN.
In England during ten years (from 1857 to 1866) the average number of
children born alive yearly was 707,120, in the proportion of 104.5 males to
100 females. But in 1857 the male births throughout England were as 105.2,
and in 1865 as 104.0 to 100. Looking to separate districts, in
Buckinghamshire (where about 5000 children are annually born) the MEAN
proportion of male to female births, during the whole period of the above
ten years, was as 102.8 to 100; whilst in N. Wales (where the average
annual births are 12,873) it was as high as 106.2 to 100. Taking a still
smaller district, viz., Rutlandshire (where the annual births average only
739), in 1864 the male births were as 114.6, and in 1862 as only 97.0 to
100; but even in this small district the average of the 7385 births during
the whole ten years, was as 104.5 to 100: that is in the same ratio as
throughout England. (48. 'Twenty-ninth Annual Report of the Registrar-
General for 1866.' In this report (p. xii.) a special decennial table is
given.) The proportions are sometimes slightly disturbed by unknown
causes; thus Prof. Faye states "that in some districts of Norway there has
been during a decennial period a steady deficiency of boys, whilst in
others the opposite condition has existed." In France during forty-four
years the male to the female births have been as 106.2 to 100; but during
this period it has occurred five times in one department, and six times in
another, that the female births have exceeded the males. In Russia the
average proportion is as high as 108.9, and in Philadelphia in the United
States as 110.5 to 100. (49. For Norway and Russia, see abstract of Prof.
Faye's researches, in 'British and Foreign Medico-Chirurg. Review,' April
1867, pp. 343, 345. For France, the 'Annuaire pour l'An 1867,' p. 213.
For Philadelphia, Dr. Stockton Hough, 'Social Science Assoc.' 1874. For
the Cape of Good Hope, Quetelet as quoted by Dr. H.H. Zouteveen, in the
Dutch Translation of this work (vol. i. p. 417), where much information is
given on the proportion of the sexes.) The average for Europe, deduced by
Bickes from about seventy million births, is 106 males to 100 females. On
the other hand, with white children born at the Cape of Good Hope, the
proportion of males is so low as to fluctuate during successive years
between 90 and 99 males for every 100 females. It is a singular fact that
with Jews the proportion of male births is decidedly larger than with
Christians: thus in Prussia the proportion is as 113, in Breslau as 114,
and in Livonia as 120 to 100; the Christian births in these countries being
the same as usual, for instance, in Livonia as 104 to 100. (50. In regard
to the Jews, see M. Thury, 'La Loi de Production des Sexes,' 1863, p. 25.)
Prof. Faye remarks that "a still greater preponderance of males would be
met with, if death struck both sexes in equal proportion in the womb and
during birth. But the fact is, that for every 100 still-born females, we
have in several countries from 134.6 to 144.9 still-born males. During the
first four or five years of life, also, more male children die than
females, for example in England, during the first year, 126 boys die for
every 100 girls--a proportion which in France is still more unfavourable."
(51. 'British and Foreign Medico-Chirurg. Review,' April 1867, p. 343.
Dr. Stark also remarks ('Tenth Annual Report of Births, Deaths, etc., in
Scotland,' 1867, p. xxviii.) that "These examples may suffice to show that,
at almost every stage of life, the males in Scotland have a greater
liability to death and a higher death-rate than the females. The fact,
however, of this peculiarity being most strongly developed at that
infantile period of life when the dress, food, and general treatment of
both sexes are alike, seems to prove that the higher male death-rate is an
impressed, natural, and constitutional peculiarity due to sex alone.") Dr.
Stockton Hough accounts for these facts in part by the more frequent
defective development of males than of females. We have before seen that
the male sex is more variable in structure than the female; and variations
in important organs would generally be injurious. But the size of the
body, and especially of the head, being greater in male than female infants
is another cause: for the males are thus more liable to be injured during
parturition. Consequently the still-born males are more numerous; and, as
a highly competent judge, Dr. Crichton Browne (52. 'West Riding Lunatic
Asylum Reports,' vol. i. 1871, p. 8. Sir J. Simpson has proved that the
head of the male infant exceeds that of the female by 3/8ths of an inch in
circumference, and by 1/8th in transverse diameter. Quetelet has shewn
that woman is born smaller than man; see Dr. Duncan, 'Fecundity, Fertility,
and Sterility,' 1871, p. 382.), believes, male infants often suffer in
health for some years after birth. Owing to this excess in the death-rate
of male children, both at birth and for some time subsequently, and owing
to the exposure of grown men to various dangers, and to their tendency to
emigrate, the females in all old-settled countries, where statistical
records have been kept, are found to preponderate considerably over the
males. (53. With the savage Guaranys of Paraguay, according to the
accurate Azara ('Voyages dans l'Amerique merid.' tom. ii. 1809, pp. 60,
179), the women are to the men in the proportion of 14 to 13.)
It seems at first sight a mysterious fact that in different nations, under
different conditions and climates, in Naples, Prussia, Westphalia, Holland,
France, England and the United States, the excess of male over female
births is less when they are illegitimate than when legitimate. (54.
Babbage, 'Edinburgh Journal of Science,' 1829, vol. i. p. 88; also p. 90,
on still-born children. On illegitimate children in England, see 'Report
of Registrar-General for 1866,' p. xv.) This has been explained by
different writers in many different ways, as from the mothers being
generally young, from the large proportion of first pregnancies, etc. But
we have seen that male infants, from the large size of their heads, suffer
more than female infants during parturition; and as the mothers of
illegitimate children must be more liable than other women to undergo bad
labours, from various causes, such as attempts at concealment by tight
lacing, hard work, distress of mind, etc., their male infants would
proportionably suffer. And this probably is the most efficient of all the
causes of the proportion of males to females born alive being less amongst
illegitimate children than amongst the legitimate. With most animals the
greater size of the adult male than of the female, is due to the stronger
males having conquered the weaker in their struggles for the possession of
the females, and no doubt it is owing to this fact that the two sexes of at
least some animals differ in size at birth. Thus we have the curious fact
that we may attribute the more frequent deaths of male than female infants,
especially amongst the illegitimate, at least in part to sexual selection.
It has often been supposed that the relative age of the two parents
determine the sex of the offspring; and Prof. Leuckart (55. Leuckart, in
Wagner 'Handworterbuch der Phys.' B. iv. 1853, s. 774.) has advanced what
he considers sufficient evidence, with respect to man and certain
domesticated animals, that this is one important though not the sole factor
in the result. So again the period of impregnation relatively to the state
of the female has been thought by some to be the efficient cause; but
recent observations discountenance this belief. According to Dr. Stockton
Hough (56. 'Social Science Association of Philadelphia,' 1874.), the
season of the year, the poverty or wealth of the parents, residence in the
country or in cities, the crossing of foreign immigrants, etc., all
influence the proportion of the sexes. With mankind, polygamy has also
been supposed to lead to the birth of a greater proportion of female
infants; but Dr. J. Campbell (57. 'Anthropological Review,' April 1870, p.
cviii.) carefully attended to this subject in the harems of Siam, and
concludes that the proportion of male to female births is the same as from
monogamous unions. Hardly any animal has been rendered so highly
polygamous as the English race-horse, and we shall immediately see that his
male and female offspring are almost exactly equal in number. I will now
give the facts which I have collected with respect to the proportional
numbers of the sexes of various animals; and will then briefly discuss how
far selection has come into play in determining the result.
HORSES.
Mr. Tegetmeier has been so kind as to tabulate for me from the 'Racing
Calendar' the births of race-horses during a period of twenty-one years,
viz., from 1846 to 1867; 1849 being omitted, as no returns were that year
published. The total births were 25,560 (58. During eleven years a record
was kept of the number of mares which proved barren or prematurely slipped
their foals; and it deserves notice, as shewing how infertile these highly-
nurtured and rather closely-interbred animals have become, that not far
from one-third of the mares failed to produce living foals. Thus during
1866, 809 male colts and 816 female colts were born, and 743 mares failed
to produce offspring. During 1867, 836 males and 902 females were born,
and 794 mares failed.), consisting of 12,763 males and 12,797 females, or
in the proportion of 99.7 males to 100 females. As these numbers are
tolerably large, and as they are drawn from all parts of England, during
several years, we may with much confidence conclude that with the domestic
horse, or at least with the race-horse, the two sexes are produced in
almost equal numbers. The fluctuations in the proportions during
successive years are closely like those which occur with mankind, when a
small and thinly-populated area is considered; thus in 1856 the male horses
were as 107.1, and in 1867 as only 92.6 to 100 females. In the tabulated
returns the proportions vary in cycles, for the males exceeded the females
during six successive years; and the females exceeded the males during two
periods each of four years; this, however, may be accidental; at least I
can detect nothing of the kind with man in the decennial table in the
Registrar's Report for 1866.
DOGS.
During a period of twelve years, from 1857 to 1868, the births of a large
number of greyhounds, throughout England, were sent to the 'Field'
newspaper; and I am again indebted to Mr. Tegetmeier for carefully
tabulating the results. The recorded births were 6878, consisting of 3605
males and 3273 females, that is, in the proportion of 110.1 males to 100
females. The greatest fluctuations occurred in 1864, when the proportion
was as 95.3 males, and in 1867, as 116.3 males to 100 females. The above
average proportion of 110.1 to 100 is probably nearly correct in the case
of the greyhound, but whether it would hold with other domesticated breeds
is in some degree doubtful. Mr. Cupples has enquired from several great
breeders of dogs, and finds that all without exception believe that females
are produced in excess; but he suggests that this belief may have arisen
from females being less valued, and from the consequent disappointment
producing a stronger impression on the mind.
SHEEP.
The sexes of sheep are not ascertained by agriculturists until several
months after birth, at the period when the males are castrated; so that the
following returns do not give the proportions at birth. Moreover, I find
that several great breeders in Scotland, who annually raise some thousand
sheep, are firmly convinced that a larger proportion of males than of
females die during the first year or two. Therefore the proportion of
males would be somewhat larger at birth than at the age of castration.
This is a remarkable coincidence with what, as we have seen, occurs with
mankind, and both cases probably depend on the same cause. I have received
returns from four gentlemen in England who have bred Lowland sheep, chiefly
Leicesters, during the last ten to sixteen years; they amount altogether to
8965 births, consisting of 4407 males and 4558 females; that is in the
proportion of 96.7 males to 100 females. With respect to Cheviot and
black-faced sheep bred in Scotland, I have received returns from six
breeders, two of them on a large scale, chiefly for the years 1867-1869,
but some of the returns extend back to 1862. The total number recorded
amounts to 50,685, consisting of 25,071 males and 25,614 females or in the
proportion of 97.9 males to 100 females. If we take the English and Scotch
returns together, the total number amounts to 59,650, consisting of 29,478
males and 30,172 females, or as 97.7 to 100. So that with sheep at the age
of castration the females are certainly in excess of the males, but
probably this would not hold good at birth. (59. I am much indebted to
Mr. Cupples for having procured for me the above returns from Scotland, as
well as some of the following returns on cattle. Mr. R. Elliot, of
Laighwood, first called my attention to the premature deaths of the males,
--a statement subsequently confirmed by Mr. Aitchison and others. To this
latter gentleman, and to Mr. Payan, I owe my thanks for large returns as to
sheep.)
Of CATTLE I have received returns from nine gentlemen of 982 births, too
few to be trusted; these consisted of 477 bull-calves and 505 cow-calves;
i.e., in the proportion of 94.4 males to 100 females. The Rev. W.D. Fox
informs me that in 1867 out of 34 calves born on a farm in Derbyshire only
one was a bull. Mr. Harrison Weir has enquired from several breeders of
PIGS, and most of them estimate the male to the female births as about 7 to
6. This same gentleman has bred RABBITS for many years, and has noticed
that a far greater number of bucks are produced than does. But estimations
are of little value.
Of mammalia in a state of nature I have been able to learn very little. In
regard to the common rat, I have received conflicting statements. Mr. R.
Elliot, of Laighwood, informs me that a rat-catcher assured him that he had
always found the males in great excess, even with the young in the nest.
In consequence of this, Mr. Elliot himself subsequently examined some
hundred old ones, and found the statement true. Mr. F. Buckland has bred a
large number of white rats, and he also believes that the males greatly
exceed the females. In regard to Moles, it is said that "the males are
much more numerous than the females" (60. Bell, 'History of British
Quadrupeds,' p. 100.): and as the catching of these animals is a special
occupation, the statement may perhaps be trusted. Sir A. Smith, in
describing an antelope of S. Africa (61. 'Illustrations of the Zoology of
S. Africa,' 1849, pl. 29.) (Kobus ellipsiprymnus), remarks, that in the
herds of this and other species, the males are few in number compared with
the females: the natives believe that they are born in this proportion;
others believe that the younger males are expelled from the herds, and Sir
A. Smith says, that though he has himself never seen herds consisting of
young males alone, others affirm that this does occur. It appears probable
that the young when expelled from the herd, would often fall a prey to the
many beasts of prey of the country.
BIRDS.
With respect to the FOWL, I have received only one account, namely, that
out of 1001 chickens of a highly-bred stock of Cochins, reared during eight
years by Mr. Stretch, 487 proved males and 514 females; i.e., as 94.7 to
100. In regard to domestic pigeons there is good evidence either that the
males are produced in excess, or that they live longer; for these birds
invariably pair, and single males, as Mr. Tegetmeier informs me, can always
be purchased cheaper than females. Usually the two birds reared from the
two eggs laid in the same nest are a male and a female; but Mr. Harrison
Weir, who has been so large a breeder, says that he has often bred two
cocks from the same nest, and seldom two hens; moreover, the hen is
generally the weaker of the two, and more liable to perish.
With respect to birds in a state of nature, Mr. Gould and others (62.
Brehm ('Thierleben,' B. iv. s. 990) comes to the same conclusion.) are
convinced that the males are generally the more numerous; and as the young
males of many species resemble the females, the latter would naturally
appear to be the more numerous. Large numbers of pheasants are reared by
Mr. Baker of Leadenhall from eggs laid by wild birds, and he informs Mr.
Jenner Weir that four or five males to one female are generally produced.
An experienced observer remarks (63. On the authority of L. Lloyd, 'Game
Birds of Sweden,' 1867, pp. 12, 132.), that in Scandinavia the broods of
the capercailzie and black-cock contain more males than females; and that
with the Dal-ripa (a kind of ptarmigan) more males than females attend the
leks or places of courtship; but this latter circumstance is accounted for
by some observers by a greater number of hen birds being killed by vermin.
From various facts given by White of Selborne (64. 'Nat. Hist. of
Selborne,' letter xxix. edit. of 1825, vol. i. p. 139.), it seems clear
that the males of the partridge must be in considerable excess in the south
of England; and I have been assured that this is the case in Scotland. Mr.
Weir on enquiring from the dealers, who receive at certain seasons large
numbers of ruffs (Machetes pugnax), was told that the males are much the
more numerous. This same naturalist has also enquired for me from the
birdcatchers, who annually catch an astonishing number of various small
species alive for the London market, and he was unhesitatingly answered by
an old and trustworthy man, that with the chaffinch the males are in large
excess: he thought as high as 2 males to 1 female, or at least as high as
5 to 3. (65. Mr. Jenner Weir received similar information, on making
enquiries during the following year. To shew the number of living
chaffinches caught, I may mention that in 1869 there was a match between
two experts, and one man caught in a day 62, and another 40, male
chaffinches. The greatest number ever caught by one man in a single day
was 70.) The males of the blackbird, he likewise maintained, were by far
the more numerous, whether caught by traps or by netting at night. These
statements may apparently be trusted, because this same man said that the
sexes are about equal with the lark, the twite (Linaria montana), and
goldfinch. On the other hand, he is certain that with the common linnet,
the females preponderate greatly, but unequally during different years;
during some years he has found the females to the males as four to one. It
should, however, be borne in mind, that the chief season for catching birds
does not begin till September, so that with some species partial migrations
may have begun, and the flocks at this period often consist of hens alone.
Mr. Salvin paid particular attention to the sexes of the humming-birds in
Central America, and is convinced that with most of the species the males
are in excess; thus one year he procured 204 specimens belonging to ten
species, and these consisted of 166 males and of only 38 females. With two
other species the females were in excess: but the proportions apparently
vary either during different seasons or in different localities; for on one
occasion the males of Campylopterus hemileucurus were to the females as 5
to 2, and on another occasion (66. 'Ibis,' vol. ii. p. 260, as quoted in
Gould's 'Trochilidae,' 1861, p. 52. For the foregoing proportions, I am
indebted to Mr. Salvin for a table of his results.) in exactly the reversed
ratio. As bearing on this latter point, I may add, that Mr. Powys found in
Corfu and Epirus the sexes of the chaffinch keeping apart, and "the females
by far the most numerous"; whilst in Palestine Mr. Tristram found "the male
flocks appearing greatly to exceed the female in number." (67. 'Ibis,'
1860, p. 137; and 1867, p. 369.) So again with the Quiscalus major, Mr. G.
Taylor says, that in Florida there were "very few females in proportion to
the males," (68. 'Ibis,' 1862, p. 187.) whilst in Honduras the proportion
was the other way, the species there having the character of a polygamist.
FISH.
With fish the proportional numbers of the sexes can be ascertained only by
catching them in the adult or nearly adult state; and there are many
difficulties in arriving at any just conclusion. (69. Leuckart quotes
Bloch (Wagner, 'Handworterbuch der Phys.' B. iv. 1853, s. 775), that with
fish there are twice as many males as females.) Infertile females might
readily be mistaken for males, as Dr. Gunther has remarked to me in regard
to trout. With some species the males are believed to die soon after
fertilising the ova. With many species the males are of much smaller size
than the females, so that a large number of males would escape from the
same net by which the females were caught. M. Carbonnier (70. Quoted in
the 'Farmer,' March 18, 1869, p. 369.), who has especially attended to the
natural history of the pike (Esox lucius), states that many males, owing to
their small size, are devoured by the larger females; and he believes that
the males of almost all fish are exposed from this same cause to greater
danger than the females. Nevertheless, in the few cases in which the
proportional numbers have been actually observed, the males appear to be
largely in excess. Thus Mr. R. Buist, the superintendent of the
Stormontfield experiments, says that in 1865, out of 70 salmon first landed
for the purpose of obtaining the ova, upwards of 60 were males. In 1867 he
again "calls attention to the vast disproportion of the males to the
females. We had at the outset at least ten males to one female."
Afterwards females sufficient for obtaining ova were procured. He adds,
"from the great proportion of the males, they are constantly fighting and
tearing each other on the spawning-beds." (71. 'The Stormontfield
Piscicultural Experiments,' 1866, p. 23. The 'Field' newspaper, June 29,
1867.) This disproportion, no doubt, can be accounted for in part, but
whether wholly is doubtful, by the males ascending the rivers before the
females. Mr. F. Buckland remarks in regard to trout, that "it is a curious
fact that the males preponderate very largely in number over the females.
It INVARIABLY happens that when the first rush of fish is made to the net,
there will be at least seven or eight males to one female found captive. I
cannot quite account for this; either the males are more numerous than the
females, or the latter seek safety by concealment rather than flight." He
then adds, that by carefully searching the banks sufficient females for
obtaining ova can be found. (72. 'Land and Water,' 1868, p. 41.) Mr. H.
Lee informs me that out of 212 trout, taken for this purpose in Lord
Portsmouth's park, 150 were males and 62 females.
The males of the Cyprinidae likewise seem to be in excess; but several
members of this Family, viz., the carp, tench, bream and minnow, appear
regularly to follow the practice, rare in the animal kingdom, of polyandry;
for the female whilst spawning is always attended by two males, one on each
side, and in the case of the bream by three or four males. This fact is so
well known, that it is always recommended to stock a pond with two male
tenches to one female, or at least with three males to two females. With
the minnow, an excellent observer states, that on the spawning-beds the
males are ten times as numerous as the females; when a female comes amongst
the males, "she is immediately pressed closely by a male on each side; and
when they have been in that situation for a time, are superseded by other
two males." (73. Yarrell, 'Hist. British Fishes,' vol. i. 1826, p. 307;
on the Cyprinus carpio, p. 331; on the Tinca vulgaris, p. 331; on the
Abramis brama, p. 336. See, for the minnow (Leuciscus phoxinus), 'Loudon's
Magazine of Natural History,' vol. v. 1832, p. 682.)
INSECTS.
In this great Class, the Lepidoptera almost alone afford means for judging
of the proportional numbers of the sexes; for they have been collected with
special care by many good observers, and have been largely bred from the
egg or caterpillar state. I had hoped that some breeders of silk-moths
might have kept an exact record, but after writing to France and Italy, and
consulting various treatises, I cannot find that this has ever been done.
The general opinion appears to be that the sexes are nearly equal, but in
Italy, as I hear from Professor Canestrini, many breeders are convinced
that the females are produced in excess. This same naturalist, however,
informs me, that in the two yearly broods of the Ailanthus silk-moth
(Bombyx cynthia), the males greatly preponderate in the first, whilst in
the second the two sexes are nearly equal, or the females rather in excess.
In regard to Butterflies in a state of nature, several observers have been
much struck by the apparently enormous preponderance of the males. (74.
Leuckart quotes Meinecke (Wagner, 'Handworterbuch der Phys.' B. iv. 1853,
s. 775) that the males of Butterflies are three or four times as numerous
as the females.) Thus Mr. Bates (75. 'The Naturalist on the Amazons,'
vol. ii. 1863, pp. 228, 347.), in speaking of several species, about a
hundred in number, which inhabit the upper Amazons, says that the males are
much more numerous than the females, even in the proportion of a hundred to
one. In North America, Edwards, who had great experience, estimates in the
genus Papilio the males to the females as four to one; and Mr. Walsh, who
informed me of this statement, says that with P. turnus this is certainly
the case. In South Africa, Mr. R. Trimen found the males in excess in 19
species (76. Four of these cases are given by Mr. Trimen in his
'Rhopalocera Africae Australis.'); and in one of these, which swarms in
open places, he estimated the number of males as fifty to one female. With
another species, in which the males are numerous in certain localities, he
collected only five females during seven years. In the island of Bourbon,
M. Maillard states that the males of one species of Papilio are twenty
times as numerous as the females. (77. Quoted by Trimen, 'Transactions of
the Ent. Society,' vol. v. part iv. 1866, p. 330.) Mr. Trimen informs me
that as far as he has himself seen, or heard from others, it is rare for
the females of any butterfly to exceed the males in number; but three South
African species perhaps offer an exception. Mr. Wallace (78.
'Transactions, Linnean Society,' vol. xxv. p. 37.) states that the females
of Ornithoptera croesus, in the Malay archipelago, are more common and more
easily caught than the males; but this is a rare butterfly. I may here
add, that in Hyperythra, a genus of moths, Guenee says, that from four to
five females are sent in collections from India for one male.
When this subject of the proportional numbers of the sexes of insects was
brought before the Entomological Society (79. 'Proceedings, Entomological
Society,' Feb. 17, 1868.), it was generally admitted that the males of most
Lepidoptera, in the adult or imago state, are caught in greater numbers
than the females: but this fact was attributed by various observers to the
more retiring habits of the females, and to the males emerging earlier from
the cocoon. This latter circumstance is well known to occur with most
Lepidoptera, as well as with other insects. So that, as M. Personnat
remarks, the males of the domesticated Bombyx Yamamai, are useless at the
beginning of the season, and the females at the end, from the want of
mates. (80. Quoted by Dr. Wallace in 'Proceedings, Entomological
Society,' 3rd series, vol. v. 1867, p. 487.) I cannot, however, persuade
myself that these causes suffice to explain the great excess of males, in
the above cases of certain butterflies which are extremely common in their
native countries. Mr. Stainton, who has paid very close attention during
many years to the smaller moths, informs me that when he collected them in
the imago state, he thought that the males were ten times as numerous as
the females, but that since he has reared them on a large scale from the
caterpillar state, he is convinced that the females are the more numerous.
Several entomologists concur in this view. Mr. Doubleday, however, and
some others, take an opposite view, and are convinced that they have reared
from the eggs and caterpillars a larger proportion of males than of
females.
Besides the more active habits of the males, their earlier emergence from
the cocoon, and in some cases their frequenting more open stations, other
causes may be assigned for an apparent or real difference in the
proportional numbers of the sexes of Lepidoptera, when captured in the
imago state, and when reared from the egg or caterpillar state. I hear
from Professor Canestrini, that it is believed by many breeders in Italy,
that the female caterpillar of the silk-moth suffers more from the recent
disease than the male; and Dr. Staudinger informs me that in rearing
Lepidoptera more females die in the cocoon than males. With many species
the female caterpillar is larger than the male, and a collector would
naturally choose the finest specimens, and thus unintentionally collect a
larger number of females. Three collectors have told me that this was
their practice; but Dr. Wallace is sure that most collectors take all the
specimens which they can find of the rarer kinds, which alone are worth the
trouble of rearing. Birds when surrounded by caterpillars would probably
devour the largest; and Professor Canestrini informs me that in Italy some
breeders believe, though on insufficient evidence, that in the first broods
of the Ailanthus silk-moth, the wasps destroy a larger number of the female
than of the male caterpillars. Dr. Wallace further remarks that female
caterpillars, from being larger than the males, require more time for their
development, and consume more food and moisture: and thus they would be
exposed during a longer time to danger from ichneumons, birds, etc., and in
times of scarcity would perish in greater numbers. Hence it appears quite
possible that in a state of nature, fewer female Lepidoptera may reach
maturity than males; and for our special object we are concerned with their
relative numbers at maturity, when the sexes are ready to propagate their
kind.
The manner in which the males of certain moths congregate in extraordinary
numbers round a single female, apparently indicates a great excess of
males, though this fact may perhaps be accounted for by the earlier
emergence of the males from their cocoons. Mr. Stainton informs me that
from twelve to twenty males, may often be seen congregated round a female
Elachista rufocinerea. It is well known that if a virgin Lasiocampa
quercus or Saturnia carpini be exposed in a cage, vast numbers of males
collect round her, and if confined in a room will even come down the
chimney to her. Mr. Doubleday believes that he has seen from fifty to a
hundred males of both these species attracted in the course of a single day
by a female in confinement. In the Isle of Wight Mr. Trimen exposed a box
in which a female of the Lasiocampa had been confined on the previous day,
and five males soon endeavoured to gain admittance. In Australia, Mr.
Verreaux, having placed the female of a small Bombyx in a box in his
pocket, was followed by a crowd of males, so that about 200 entered the
house with him. (81. Blanchard, 'Metamorphoses, Moeurs des Insectes,'
1868, pp. 225-226.)
Mr. Doubleday has called my attention to M. Staudinger's (82.
'Lepidopteren-Doubletten Liste,' Berlin, No. x. 1866.) list of Lepidoptera,
which gives the prices of the males and females of 300 species or well-
marked varieties of butterflies (Rhopalocera). The prices for both sexes
of the very common species are of course the same; but in 114 of the rarer
species they differ; the males being in all cases, excepting one, the
cheaper. On an average of the prices of the 113 species, the price of the
male to that of the female is as 100 to 149; and this apparently indicates
that inversely the males exceed the females in the same proportion. About
2000 species or varieties of moths (Heterocera) are catalogued, those with
wingless females being here excluded on account of the difference in habits
between the two sexes: of these 2000 species, 141 differ in price
according to sex, the males of 130 being cheaper, and those of only 11
being dearer than the females. The average price of the males of the 130
species, to that of the females, is as 100 to 143. With respect to the
butterflies in this priced list, Mr. Doubleday thinks (and no man in
England has had more experience), that there is nothing in the habits of
the species which can account for the difference in the prices of the two
sexes, and that it can be accounted for only by an excess in the number of
the males. But I am bound to add that Dr. Staudinger informs me, that he
is himself of a different opinion. He thinks that the less active habits
of the females and the earlier emergence of the males will account for his
collectors securing a larger number of males than of females, and
consequently for the lower prices of the former. With respect to specimens
reared from the caterpillar-state, Dr. Staudinger believes, as previously
stated, that a greater number of females than of males die whilst confined
to the cocoons. He adds that with certain species one sex seems to
preponderate over the other during certain years.
Of direct observations on the sexes of Lepidoptera, reared either from eggs
or caterpillars, I have received only the few following cases: (See
following table.)
So that in these eight lots of cocoons and eggs, males were produced in
excess. Taken together the proportion of males is as 122.7 to 100 females.
But the numbers are hardly large enough to be trustworthy.
On the whole, from these various sources of evidence, all pointing in the
same direction, I infer that with most species of Lepidoptera, the mature
males generally exceed the females in number, whatever the proportions may
be at their first emergence from the egg.
Males Females
The Rev. J. Hellins* of Exeter reared, during
1868, imagos of 73 species, which
consisted of 153 137
Mr. Albert Jones of Eltham reared, during
1868, imagos of 9 species, which
consisted of 159 126
During 1869 he reared imagos from 4 species
consisting of 114 112
Mr. Buckler of Emsworth, Hants, during 1869,
reared imagos from 74 species,
consisting of 180 169
Dr. Wallace of Colchester reared from one
brood of Bombyx cynthia 52 48
Dr. Wallace raised, from cocoons of Bombyx
Pernyi sent from China, during 1869 224 123
Dr. Wallace raised, during 1868 and 1869, from
two lots of cocoons of Bombyx yamamai 52 46
Total 934 761
(*83. This naturalist has been so kind as to send me some results from
former years, in which the females seemed to preponderate; but so many of
the figures were estimates, that I found it impossible to tabulate them.)
With reference to the other Orders of insects, I have been able to collect
very little reliable information. With the stag-beetle (Lucanus cervus)
"the males appear to be much more numerous than the females"; but when, as
Cornelius remarked during 1867, an unusual number of these beetles appeared
in one part of Germany, the females appeared to exceed the males as six to
one. With one of the Elateridae, the males are said to be much more
numerous than the females, and "two or three are often found united with
one female (84. Gunther's 'Record of Zoological Literature,' 1867, p. 260.
On the excess of female Lucanus, ibid, p. 250. On the males of Lucanus in
England, Westwood,' 'Modern Classification of Insects,' vol. i. p. 187. On
the Siagonium, ibid. p. 172.); so that here polyandry seems to prevail."
With Siagonium (Staphylinidae), in which the males are furnished with
horns, "the females are far more numerous than the opposite sex." Mr.
Janson stated at the Entomological Society that the females of the bark
feeding Tomicus villosus are so common as to be a plague, whilst the males
are so rare as to be hardly known.
It is hardly worth while saying anything about the proportion of the sexes
in certain species and even groups of insects, for the males are unknown or
very rare, and the females are parthenogenetic, that is, fertile without
sexual union; examples of this are afforded by several of the Cynipidae.
(85. Walsh in 'The American Entomologist,' vol. i. 1869, p. 103. F.
Smith, 'Record of Zoological Lit.' 1867, p. 328.) In all the gall-making
Cynipidae known to Mr. Walsh, the females are four or five times as
numerous as the males; and so it is, as he informs me, with the gall-making
Cecidomyiidae (Diptera). With some common species of Saw-flies
(Tenthredinae) Mr. F. Smith has reared hundreds of specimens from larvae of
all sizes, but has never reared a single male; on the other hand, Curtis
says (86. 'Farm Insects,' pp. 45-46.), that with certain species
(Athalia), bred by him, the males were to the females as six to one; whilst
exactly the reverse occurred with the mature insects of the same species
caught in the fields. In the family of bees, Hermann Muller (87.
'Anwendung der Darwin'schen Lehre,' Verh. d. n. Jahrg., xxiv.), collected a
large number of specimens of many species, and reared others from the
cocoons, and counted the sexes. He found that the males of some species
greatly exceeded the females in number; in others the reverse occurred; and
in others the two sexes were nearly equal. But as in most cases the males
emerge from the cocoons before the females, they are at the commencement of
the breeding-season practically in excess. Muller also observed that the
relative number of the two sexes in some species differed much in different
localities. But as H. Muller has himself remarked to me, these remarks
must be received with some caution, as one sex might more easily escape
observation than the other. Thus his brother Fritz Muller has noticed in
Brazil that the two sexes of the same species of bee sometimes frequent
different kinds of flowers. With respect to the Orthoptera, I know hardly
anything about the relative number of the sexes: Korte (88. 'Die Strich,
Zug oder Wanderheuschrecke,' 1828, p. 20.), however, says that out of 500
locusts which he examined, the males were to the females as five to six.
With the Neuroptera, Mr. Walsh states that in many, but by no means in all
the species of the Odonatous group, there is a great overplus of males: in
the genus Hetaerina, also, the males are generally at least four times as
numerous as the females. In certain species in the genus Gomphus the males
are equally in excess, whilst in two other species, the females are twice
or thrice as numerous as the males. In some European species of Psocus
thousands of females may be collected without a single male, whilst with
other species of the same genus both sexes are common. (89. 'Observations
on N. American Neuroptera,' by H. Hagen and B.D. Walsh, 'Proceedings, Ent.
Soc. Philadelphia,' Oct. 1863, pp. 168, 223, 239.) In England, Mr.
MacLachlan has captured hundreds of the female Apatania muliebris, but has
never seen the male; and of Boreus hyemalis only four or five males have
been seen here. (90. 'Proceedings, Ent. Soc. London,' Feb. 17, 1868.)
With most of these species (excepting the Tenthredinae) there is at present
no evidence that the females are subject to parthenogenesis; and thus we
see how ignorant we are of the causes of the apparent discrepancy in the
proportion of the two sexes.
In the other classes of the Articulata I have been able to collect still
less information. With spiders, Mr. Blackwall, who has carefully attended
to this class during many years, writes to me that the males from their
more erratic habits are more commonly seen, and therefore appear more
numerous. This is actually the case with a few species; but he mentions
several species in six genera, in which the females appear to be much more
numerous than the males. (91. Another great authority with respect to
this class, Prof. Thorell of Upsala ('On European Spiders,' 1869-70, part
i. p. 205), speaks as if female spiders were generally commoner than the
males.) The small size of the males in comparison with the females (a
peculiarity which is sometimes carried to an extreme degree), and their
widely different appearance, may account in some instances for their rarity
in collections. (92. See, on this subject, Mr. O.P. Cambridge, as quoted
in 'Quarterly Journal of Science,' 1868, page 429.)
Some of the lower Crustaceans are able to propagate their kind sexually,
and this will account for the extreme rarity of the males; thus von Siebold
(93. 'Beitrage zur Parthenogenesis,' p. 174.) carefully examined no less
than 13,000 specimens of Apus from twenty-one localities, and amongst these
he found only 319 males. With some other forms (as Tanais and Cypris), as
Fritz Muller informs me, there is reason to believe that the males are much
shorter-lived than the females; and this would explain their scarcity,
supposing the two sexes to be at first equal in number. On the other hand,
Muller has invariably taken far more males than females of the Diastylidae
and of Cypridina on the shores of Brazil: thus with a species in the
latter genus, 63 specimens caught the same day included 57 males; but he
suggests that this preponderance may be due to some unknown difference in
the habits of the two sexes. With one of the higher Brazilian crabs,
namely a Gelasimus, Fritz Muller found the males to be more numerous than
the females. According to the large experience of Mr. C. Spence Bate, the
reverse seems to be the case with six common British crabs, the names of
which he has given me.
THE PROPORTION OF THE SEXES IN RELATION TO NATURAL SELECTION.
There is reason to suspect that in some cases man has by selection
indirectly influenced his own sex-producing powers. Certain women tend to
produce during their whole lives more children of one sex than of the
other: and the same holds good of many animals, for instance, cows and
horses; thus Mr. Wright of Yeldersley House informs me that one of his Arab
mares, though put seven times to different horses, produced seven fillies.
Though I have very little evidence on this head, analogy would lead to the
belief, that the tendency to produce either sex would be inherited like
almost every other peculiarity, for instance, that of producing twins; and
concerning the above tendency a good authority, Mr. J. Downing, has
communicated to me facts which seem to prove that this does occur in
certain families of short-horn cattle. Col. Marshall (94. 'The Todas,'
1873, pp. 100, 111, 194, 196.) has recently found on careful examination
that the Todas, a hill-tribe of India, consist of 112 males and 84 females
of all ages--that is in a ratio of 133.3 males to 100 females. The Todas,
who are polyandrous in their marriages, during former times invariably
practised female infanticide; but this practice has now been discontinued
for a considerable period. Of the children born within late years, the
males are more numerous than the females, in the proportion of 124 to 100.
Colonel Marshall accounts for this fact in the following ingenious manner.
"Let us for the purpose of illustration take three families as representing
an average of the entire tribe; say that one mother gives birth to six
daughters and no sons; a second mother has six sons only, whilst the third
mother has three sons and three daughters. The first mother, following the
tribal custom, destroys four daughters and preserves two. The second
retains her six sons. The third kills two daughters and keeps one, as also
her three sons. We have then from the three families, nine sons and three
daughters, with which to continue the breed. But whilst the males belong
to families in which the tendency to produce sons is great, the females are
of those of a converse inclination. Thus the bias strengthens with each
generation, until, as we find, families grow to have habitually more sons
than daughters."
That this result would follow from the above form of infanticide seems
almost certain; that is if we assume that a sex-producing tendency is
inherited. But as the above numbers are so extremely scanty, I have
searched for additional evidence, but cannot decide whether what I have
found is trustworthy; nevertheless the facts are, perhaps, worth giving.
The Maories of New Zealand have long practised infanticide; and Mr. Fenton
(95. 'Aboriginal Inhabitants of New Zealand: Government Report,' 1859, p.
36.) states that he "has met with instances of women who have destroyed
four, six, and even seven children, mostly females. However, the universal
testimony of those best qualified to judge, is conclusive that this custom
has for many years been almost extinct. Probably the year 1835 may be
named as the period of its ceasing to exist." Now amongst the New
Zealanders, as with the Todas, male births are considerably in excess. Mr.
Fenton remarks (p. 30), "One fact is certain, although the exact period of
the commencement of this singular condition of the disproportion of the
sexes cannot be demonstratively fixed, it is quite clear that this course
of decrease was in full operation during the years 1830 to 1844, when the
non-adult population of 1844 was being produced, and has continued with
great energy up to the present time." The following statements are taken
from Mr. Fenton (p. 26), but as the numbers are not large, and as the
census was not accurate, uniform results cannot be expected. It should be
borne in mind in this and the following cases, that the normal state of
every population is an excess of women, at least in all civilised
countries, chiefly owing to the greater mortality of the male sex during
youth, and partly to accidents of all kinds later in life. In 1858, the
native population of New Zealand was estimated as consisting of 31,667
males and 24,303 females of all ages, that is in the ratio of 130.3 males
to 100 females. But during this same year, and in certain limited
districts, the numbers were ascertained with much care, and the males of
all ages were here 753 and the females 616; that is in the ratio of 122.2
males to 100 females. It is more important for us that during this same
year of 1858, the NON-ADULT males within the same district were found to be
178, and the NON-ADULT females 142, that is in the ratio of 125.3 to 100.
It may be added that in 1844, at which period female infanticide had only
lately ceased, the NON-ADULT males in one district were 281, and the NON-
ADULT females only 194, that is in the ratio of 144.8 males to 100 females.
In the Sandwich Islands, the males exceed the females in number.
Infanticide was formerly practised there to a frightful extent, but was by
no means confined to female infants, as is shewn by Mr. Ellis (96.
'Narrative of a Tour through Hawaii,' 1826, p. 298.), and as I have been
informed by Bishop Staley and the Rev. Mr. Coan. Nevertheless, another
apparently trustworthy writer, Mr. Jarves (97. 'History of the Sandwich
Islands,' 1843, p. 93.), whose observations apply to the whole archipelago,
remarks:--"Numbers of women are to be found, who confess to the murder of
from three to six or eight children," and he adds, "females from being
considered less useful than males were more often destroyed." From what is
known to occur in other parts of the world, this statement is probable; but
must be received with much caution. The practice of infanticide ceased
about the year 1819, when idolatry was abolished and missionaries settled
in the Islands. A careful census in 1839 of the adult and taxable men and
women in the island of Kauai and in one district of Oahu (Jarves, p. 404),
gives 4723 males and 3776 females; that is in the ratio of 125.08 to 100.
At the same time the number of males under fourteen years in Kauai and
under eighteen in Oahu was 1797, and of females of the same ages 1429; and
here we have the ratio of 125.75 males to 100 females.
In a census of all the islands in 1850 (98. This is given in the Rev. H.T.
Cheever's 'Life in the Sandwich Islands,' 1851, p. 277.), the males of all
ages amount to 36,272, and the females to 33,128, or as 109.49 to 100. The
males under seventeen years amounted to 10,773, and the females under the
same age to 9593, or as 112.3 to 100. From the census of 1872, the
proportion of males of all ages (including half-castes) to females, is as
125.36 to 100. It must be borne in mind that all these returns for the
Sandwich Islands give the proportion of living males to living females, and
not of the births; and judging from all civilised countries the proportion
of males would have been considerably higher if the numbers had referred to
births. (99. Dr. Coulter, in describing ('Journal R. Geograph. Soc.' vol.
v. 1835, p. 67) the state of California about the year 1830, says that the
natives, reclaimed by the Spanish missionaries, have nearly all perished,
or are perishing, although well treated, not driven from their native land,
and kept from the use of spirits. He attributes this, in great part, to
the undoubted fact that the men greatly exceed the women in number; but he
does not know whether this is due to a failure of female offspring, or to
more females dying during early youth. The latter alternative, according
to all analogy, is very improbable. He adds that "infanticide, properly so
called, is not common, though very frequent recourse is had to abortion."
If Dr. Coulter is correct about infanticide, this case cannot be advanced
in support of Colonel Marshall's view. From the rapid decrease of the
reclaimed natives, we may suspect that, as in the cases lately given, their
fertility has been diminished from changed habits of life.
I had hoped to gain some light on this subject from the breeding of dogs;
inasmuch as in most breeds, with the exception, perhaps, of greyhounds,
many more female puppies are destroyed than males, just as with the Toda
infants. Mr. Cupples assures me that this is usual with Scotch deer-
hounds. Unfortunately, I know nothing of the proportion of the sexes in
any breed, excepting greyhounds, and there the male births are to the
females as 110.1 to 100. Now from enquiries made from many breeders, it
seems that the females are in some respects more esteemed, though otherwise
troublesome; and it does not appear that the female puppies of the best-
bred dogs are systematically destroyed more than the males, though this
does sometimes take place to a limited extent. Therefore I am unable to
decide whether we can, on the above principles, account for the
preponderance of male births in greyhounds. On the other hand, we have
seen that with horses, cattle, and sheep, which are too valuable for the
young of either sex to be destroyed, if there is any difference, the
females are slightly in excess.)
From the several foregoing cases we have some reason to believe that
infanticide practised in the manner above explained, tends to make a male-
producing race; but I am far from supposing that this practice in the case
of man, or some analogous process with other species, has been the sole
determining cause of an excess of males. There may be some unknown law
leading to this result in decreasing races, which have already become
somewhat infertile. Besides the several causes previously alluded to, the
greater facility of parturition amongst savages, and the less consequent
injury to their male infants, would tend to increase the proportion of
live-born males to females. There does not, however, seem to be any
necessary connection between savage life and a marked excess of males; that
is if we may judge by the character of the scanty offspring of the lately
existing Tasmanians and of the crossed offspring of the Tahitians now
inhabiting Norfolk Island.
As the males and females of many animals differ somewhat in habits and are
exposed in different degrees to danger, it is probable that in many cases,
more of one sex than of the other are habitually destroyed. But as far as
I can trace out the complication of causes, an indiscriminate though large
destruction of either sex would not tend to modify the sex-producing power
of the species. With strictly social animals, such as bees or ants, which
produce a vast number of sterile and fertile females in comparison with the
males, and to whom this preponderance is of paramount importance, we can
see that those communities would flourish best which contained females
having a strong inherited tendency to produce more and more females; and in
such cases an unequal sex-producing tendency would be ultimately gained
through natural selection. With animals living in herds or troops, in
which the males come to the front and defend the herd, as with the bisons
of North America and certain baboons, it is conceivable that a male-
producing tendency might be gained by natural selection; for the
individuals of the better defended herds would leave more numerous
descendants. In the case of mankind the advantage arising from having a
preponderance of men in the tribe is supposed to be one chief cause of the
practice of female infanticide.
In no case, as far as we can see, would an inherited tendency to produce
both sexes in equal numbers or to produce one sex in excess, be a direct
advantage or disadvantage to certain individuals more than to others; for
instance, an individual with a tendency to produce more males than females
would not succeed better in the battle for life than an individual with an
opposite tendency; and therefore a tendency of this kind could not be
gained through natural selection. Nevertheless, there are certain animals
(for instance, fishes and cirripedes) in which two or more males appear to
be necessary for the fertilisation of the female; and the males accordingly
largely preponderate, but it is by no means obvious how this male-producing
tendency could have been acquired. I formerly thought that when a tendency
to produce the two sexes in equal numbers was advantageous to the species,
it would follow from natural selection, but I now see that the whole
problem is so intricate that it is safer to leave its solution for the
future.
CHAPTER IX.
SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.
These characters absent in the lowest classes--Brilliant colours--Mollusca
--Annelids--Crustacea, secondary sexual characters strongly developed;
dimorphism; colour; characters not acquired before maturity--Spiders,
sexual colours of; stridulation by the males--Myriapoda.
With animals belonging to the lower classes, the two sexes are not rarely
united in the same individual, and therefore secondary sexual characters
cannot be developed. In many cases where the sexes are separate, both are
permanently attached to some support, and the one cannot search or struggle
for the other. Moreover it is almost certain that these animals have too
imperfect senses and much too low mental powers to appreciate each other's
beauty or other attractions, or to feel rivalry.
Hence in these classes or sub-kingdoms, such as the Protozoa, Coelenterata,
Echinodermata, Scolecida, secondary sexual characters, of the kind which we
have to consider, do not occur: and this fact agrees with the belief that
such characters in the higher classes have been acquired through sexual
selection, which depends on the will, desire, and choice of either sex.
Nevertheless some few apparent exceptions occur; thus, as I hear from Dr.
Baird, the males of certain Entozoa, or internal parasitic worms, differ
slightly in colour from the females; but we have no reason to suppose that
such differences have been augmented through sexual selection.
Contrivances by which the male holds the female, and which are
indispensable for the propagation of the species, are independent of sexual
selection, and have been acquired through ordinary selection.
Many of the lower animals, whether hermaphrodites or with separate sexes,
are ornamented with the most brilliant tints, or are shaded and striped in
an elegant manner; for instance, many corals and sea-anemones (Actiniae),
some jelly-fish (Medusae, Porpita, etc.), some Planariae, many star-fishes,
Echini, Ascidians, etc.; but we may conclude from the reasons already
indicated, namely, the union of the two sexes in some of these animals, the
permanently affixed condition of others, and the low mental powers of all,
that such colours do not serve as a sexual attraction, and have not been
acquired through sexual selection. It should be borne in mind that in no
case have we sufficient evidence that colours have been thus acquired,
except where one sex is much more brilliantly or conspicuously coloured
than the other, and where there is no difference in habits between the
sexes sufficient to account for their different colours. But the evidence
is rendered as complete as it can ever be, only when the more ornamented
individuals, almost always the males, voluntarily display their attractions
before the other sex; for we cannot believe that such display is useless,
and if it be advantageous, sexual selection will almost inevitably follow.
We may, however, extend this conclusion to both sexes, when coloured alike,
if their colours are plainly analogous to those of one sex alone in certain
other species of the same group.
How, then, are we to account for the beautiful or even gorgeous colours of
many animals in the lowest classes? It appears doubtful whether such
colours often serve as a protection; but that we may easily err on this
head, will be admitted by every one who reads Mr. Wallace's excellent essay
on this subject. It would not, for instance, at first occur to any one
that the transparency of the Medusae, or jelly-fish, is of the highest
service to them as a protection; but when we are reminded by Haeckel that
not only the Medusae, but many floating Mollusca, crustaceans, and even
small oceanic fishes partake of this same glass-like appearance, often
accompanied by prismatic colours, we can hardly doubt that they thus escape
the notice of pelagic birds and other enemies. M. Giard is also convinced
(1. 'Archives de Zoolog. Exper.' Oct. 1872, p. 563.) that the bright tints
of certain sponges and ascidians serve as a protection. Conspicuous
colours are likewise beneficial to many animals as a warning to their
would-be devourers that they are distasteful, or that they possess some
special means of defence; but this subject will be discussed more
conveniently hereafter.
We can, in our ignorance of most of the lowest animals, only say that their
bright tints result either from the chemical nature or the minute structure
of their tissues, independently of any benefit thus derived. Hardly any
colour is finer than that of arterial blood; but there is no reason to
suppose that the colour of the blood is in itself any advantage; and though
it adds to the beauty of the maiden's cheek, no one will pretend that it
has been acquired for this purpose. So again with many animals, especially
the lower ones, the bile is richly coloured; thus, as I am informed by Mr.
Hancock, the extreme beauty of the Eolidae (naked sea-slugs) is chiefly due
to the biliary glands being seen through the translucent integuments--this
beauty being probably of no service to these animals. The tints of the
decaying leaves in an American forest are described by every one as
gorgeous; yet no one supposes that these tints are of the least advantage
to the trees. Bearing in mind how many substances closely analogous to
natural organic compounds have been recently formed by chemists, and which
exhibit the most splendid colours, it would have been a strange fact if
substances similarly coloured had not often originated, independently of
any useful end thus gained, in the complex laboratory of living organisms.
THE SUB-KINGDOM OF THE MOLLUSCA.
Throughout this great division of the animal kingdom, as far as I can
discover, secondary sexual characters, such as we are here considering,
never occur. Nor could they be expected in the three lowest classes,
namely, in the Ascidians, Polyzoa, and Brachiopods (constituting the
Molluscoida of some authors), for most of these animals are permanently
affixed to a support or have their sexes united in the same individual. In
the Lamellibranchiata, or bivalve shells, hermaphroditism is not rare. In
the next higher class of the Gasteropoda, or univalve shells, the sexes are
either united or separate. But in the latter case the males never possess
special organs for finding, securing, or charming the females, or for
fighting with other males. As I am informed by Mr. Gwyn Jeffreys, the sole
external difference between the sexes consists in the shell sometimes
differing a little in form; for instance, the shell of the male periwinkle
(Littorina littorea) is narrower and has a more elongated spire than that
of the female. But differences of this nature, it may be presumed, are
directly connected with the act of reproduction, or with the development of
the ova.
The Gasteropoda, though capable of locomotion and furnished with imperfect
eyes, do not appear to be endowed with sufficient mental powers for the
members of the same sex to struggle together in rivalry, and thus to
acquire secondary sexual characters. Nevertheless with the pulmoniferous
gasteropods, or land-snails, the pairing is preceded by courtship; for
these animals, though hermaphrodites, are compelled by their structure to
pair together. Agassiz remarks, "Quiconque a eu l'occasion d'observer les
amours des limacons, ne saurait mettre en doute la seduction deployee dans
les mouvements et les allures qui preparent et accomplissent le double
embrassement de ces hermaphrodites." (2. 'De l'Espece et de la Class.'
etc., 1869, p. 106.) These animals appear also susceptible of some degree
of permanent attachment: an accurate observer, Mr. Lonsdale, informs me
that he placed a pair of land-snails, (Helix pomatia), one of which was
weakly, into a small and ill-provided garden. After a short time the
strong and healthy individual disappeared, and was traced by its track of
slime over a wall into an adjoining well-stocked garden. Mr. Lonsdale
concluded that it had deserted its sickly mate; but after an absence of
twenty-four hours it returned, and apparently communicated the result of
its successful exploration, for both then started along the same track and
disappeared over the wall.
Even in the highest class of the Mollusca, the Cephalopoda or cuttle-
fishes, in which the sexes are separate, secondary sexual characters of the
present kind do not, as far as I can discover, occur. This is a surprising
circumstance, as these animals possess highly-developed sense-organs and
have considerable mental powers, as will be admitted by every one who has
watched their artful endeavours to escape from an enemy. (3. See, for
instance, the account which I have given in my 'Journal of Researches,'
1845, p. 7.) Certain Cephalopoda, however, are characterised by one
extraordinary sexual character, namely that the male element collects
within one of the arms or tentacles, which is then cast off, and clinging
by its sucking-discs to the female, lives for a time an independent life.
So completely does the cast-off arm resemble a separate animal, that it was
described by Cuvier as a parasitic worm under the name of Hectocotyle. But
this marvellous structure may be classed as a primary rather than as a
secondary sexual character.
Although with the Mollusca sexual selection does not seem to have come into
play; yet many univalve and bivalve shells, such as volutes, cones,
scallops, etc., are beautifully coloured and shaped. The colours do not
appear in most cases to be of any use as a protection; they are probably
the direct result, as in the lowest classes, of the nature of the tissues;
the patterns and the sculpture of the shell depending on its manner of
growth. The amount of light seems to be influential to a certain extent;
for although, as repeatedly stated by Mr. Gwyn Jeffreys, the shells of some
species living at a profound depth are brightly coloured, yet we generally
see the lower surfaces, as well as the parts covered by the mantle, less
highly-coloured than the upper and exposed surfaces. (4. I have given
('Geological Observations on Volcanic Islands,' 1844, p. 53) a curious
instance of the influence of light on the colours of a frondescent
incrustation, deposited by the surf on the coast-rocks of Ascension and
formed by the solution of triturated sea-shells.) In some cases, as with
shells living amongst corals or brightly-tinted seaweeds, the bright
colours may serve as a protection. (5. Dr. Morse has lately discussed
this subject in his paper on the 'Adaptive Coloration of Mollusca,' 'Proc.
Boston Soc. of Nat. Hist.' vol. xiv. April 1871.) But that many of the
nudibranch Mollusca, or sea-slugs, are as beautifully coloured as any
shells, may be seen in Messrs. Alder and Hancock's magnificent work; and
from information kindly given me by Mr. Hancock, it seems extremely
doubtful whether these colours usually serve as a protection. With some
species this may be the case, as with one kind which lives on the green
leaves of algae, and is itself bright-green. But many brightly-coloured,
white, or otherwise conspicuous species, do not seek concealment; whilst
again some equally conspicuous species, as well as other dull-coloured
kinds live under stones and in dark recesses. So that with these
nudibranch molluscs, colour apparently does not stand in any close relation
to the nature of the places which they inhabit.
These naked sea-slugs are hermaphrodites, yet they pair together, as do
land-snails, many of which have extremely pretty shells. It is conceivable
that two hermaphrodites, attracted by each other's greater beauty, might
unite and leave offspring which would inherit their parents' greater
beauty. But with such lowly-organised creatures this is extremely
improbable. Nor is it at all obvious how the offspring from the more
beautiful pairs of hermaphrodites would have any advantage over the
offspring of the less beautiful, so as to increase in number, unless indeed
vigour and beauty generally coincided. We have not here the case of a
number of males becoming mature before the females, with the more beautiful
males selected by the more vigorous females. If, indeed, brilliant colours
were beneficial to a hermaphrodite animal in relation to its general habits
of life, the more brightly-tinted individuals would succeed best and would
increase in number; but this would be a case of natural and not of sexual
selection.
SUB-KINGDOM OF THE VERMES: CLASS, ANNELIDA (OR SEA-WORMS).
In this class, although the sexes, when separate, sometimes differ from
each other in characters of such importance that they have been placed
under distinct genera or even families, yet the differences do not seem of
the kind which can be safely attributed to sexual selection. These animals
are often beautifully coloured, but as the sexes do not differ in this
respect, we are but little concerned with them. Even the Nemertians,
though so lowly organised, "vie in beauty and variety of colouring with any
other group in the invertebrate series"; yet Dr. McIntosh (6. See his
beautiful monograph on 'British Annelids,' part i. 1873, p. 3.) cannot
discover that these colours are of any service. The sedentary annelids
become duller-coloured, according to M. Quatrefages (7. See M. Perrier:
'L'Origine de l'Homme d'apres Darwin,' 'Revue Scientifique', Feb. 1873, p.
866.), after the period of reproduction; and this I presume may be
attributed to their less vigorous condition at that time. All these worm-
like animals apparently stand too low in the scale for the individuals of
either sex to exert any choice in selecting a partner, or for the
individuals of the same sex to struggle together in rivalry.
SUB-KINGDOM OF THE ARTHROPODA: CLASS, CRUSTACEA.
In this great class we first meet with undoubted secondary sexual
characters, often developed in a remarkable manner. Unfortunately the
habits of crustaceans are very imperfectly known, and we cannot explain the
uses of many structures peculiar to one sex. With the lower parasitic
species the males are of small size, and they alone are furnished with
perfect swimming-legs, antennae and sense-organs; the females being
destitute of these organs, with their bodies often consisting of a mere
distorted mass. But these extraordinary differences between the two sexes
are no doubt related to their widely different habits of life, and
consequently do not concern us. In various crustaceans, belonging to
distinct families, the anterior antennae are furnished with peculiar
thread-like bodies, which are believed to act as smelling-organs, and these
are much more numerous in the males than in the females. As the males,
without any unusual development of their olfactory organs, would almost
certainly be able sooner or later to find the females, the increased number
of the smelling-threads has probably been acquired through sexual
selection, by the better provided males having been the more successful in
finding partners and in producing offspring. Fritz Muller has described a
remarkable dimorphic species of Tanais, in which the male is represented by
two distinct forms, which never graduate into each other. In the one form
the male is furnished with more numerous smelling-threads, and in the other
form with more powerful and more elongated chelae or pincers, which serve
to hold the female. Fritz Muller suggests that these differences between
the two male forms of the same species may have originated in certain
individuals having varied in the number of the smelling-threads, whilst
other individuals varied in the shape and size of their chelae; so that of
the former, those which were best able to find the female, and of the
latter, those which were best able to hold her, have left the greatest
number of progeny to inherit their respective advantages. (8. 'Facts and
Arguments for Darwin,' English translat., 1869, p. 20. See the previous
discussion on the olfactory threads. Sars has described a somewhat
analogous case (as quoted in 'Nature,' 1870, p. 455) in a Norwegian
crustacean, the Pontoporeia affinis.)
[Fig.4. Labidocera Darwinii (from Lubbock). Labelled are:
a. Part of right anterior antenna of male, forming a prehensile organ.
b. Posterior pair of thoracic legs of male.
c. Ditto of female.]
In some of the lower crustaceans, the right anterior antenna of the male
differs greatly in structure from the left, the latter resembling in its
simple tapering joints the antennae of the female. In the male the
modified antenna is either swollen in the middle or angularly bent, or
converted (Fig. 4) into an elegant, and sometimes wonderfully complex,
prehensile organ. (9. See Sir J. Lubbock in 'Annals and Mag. of Nat.
Hist.' vol. xi. 1853, pl. i. and x.; and vol. xii. (1853), pl. vii. See
also Lubbock in 'Transactions, Entomological Society,' vol. iv. new series,
1856-1858, p. 8. With respect to the zigzagged antennae mentioned below,
see Fritz Muller, 'Facts and Arguments for Darwin,' 1869, p. 40, foot-
note.) It serves, as I hear from Sir J. Lubbock, to hold the female, and
for this same purpose one of the two posterior legs (b) on the same side of
the body is converted into a forceps. In another family the inferior or
posterior antennae are "curiously zigzagged" in the males alone.
[Fig. 5. Anterior part of body of Callianassa (from Milne-Edwards),
showing the unequal and differently-constructed right and left-hand chelae
of the male. N.B.--The artist by mistake has reversed the drawing, and
made the left-hand chela the largest.
Fig. 6. Second leg of male Orchestia Tucuratinga (from Fritz Muller).
Fig. 7. Ditto of female.]
In the higher crustaceans the anterior legs are developed into chelae or
pincers; and these are generally larger in the male than in the female,--so
much so that the market value of the male edible crab (Cancer pagurus),
according to Mr. C. Spence Bate, is five times as great as that of the
female. In many species the chelae are of unequal size on the opposite
side of the body, the right-hand one being, as I am informed by Mr. Bate,
generally, though not invariably, the largest. This inequality is also
often much greater in the male than in the female. The two chelae of the
male often differ in structure (Figs. 5, 6, and 7), the smaller one
resembling that of the female. What advantage is gained by their
inequality in size on the opposite sides of the body, and by the inequality
being much greater in the male than in the female; and why, when they are
of equal size, both are often much larger in the male than in the female,
is not known. As I hear from Mr. Bate, the chelae are sometimes of such
length and size that they cannot possibly be used for carrying food to the
mouth. In the males of certain fresh-water prawns (Palaemon) the right leg
is actually longer than the whole body. (10. See a paper by Mr. C. Spence
Bate, with figures, in 'Proceedings, Zoological Society,' 1868, p. 363; and
on the nomenclature of the genus, ibid. p. 585. I am greatly indebted to
Mr. Spence Bate for nearly all the above statements with respect to the
chelae of the higher crustaceans.) The great size of the one leg with its
chelae may aid the male in fighting with his rivals; but this will not
account for their inequality in the female on the opposite sides of the
body. In Gelasimus, according to a statement quoted by Milne Edwards (11.
'Hist. Nat. des Crust.' tom. ii. 1837, p. 50.), the male and the female
live in the same burrow, and this shews that they pair; the male closes the
mouth of the burrow with one of its chelae, which is enormously developed;
so that here it indirectly serves as a means of defence. Their main use,
however, is probably to seize and to secure the female, and this in some
instances, as with Gammarus, is known to be the case. The male of the
hermit or soldier crab (Pagurus) for weeks together, carries about the
shell inhabited by the female. (12. Mr. C. Spence Bate, 'British
Association, Fourth Report on the Fauna of S. Devon.') The sexes, however,
of the common shore-crab (Carcinus maenas), as Mr. Bate informs me, unite
directly after the female has moulted her hard shell, when she is so soft
that she would be injured if seized by the strong pincers of the male; but
as she is caught and carried about by the male before moulting, she could
then be seized with impunity.
[Fig.8. Orchestia Darwinii (from Fritz Muller), showing the differently-
constructed chelae of the two male forms.]
Fritz Muller states that certain species of Melita are distinguished from
all other amphipods by the females having "the coxal lamellae of the
penultimate pair of feet produced into hook-like processes, of which the
males lay hold with the hands of the first pair." The development of these
hook-like processes has probably followed from those females which were the
most securely held during the act of reproduction, having left the largest
number of offspring. Another Brazilian amphipod (see Orchestia darwinii,
Fig. 8) presents a case of dimorphism, like that of Tanais; for there are
two male forms, which differ in the structure of their chelae. (13. Fritz
Muller, 'Facts and Arguments for Darwin,' 1869, pp. 25-28.) As either
chela would certainly suffice to hold the female,--for both are now used
for this purpose,--the two male forms probably originated by some having
varied in one manner and some in another; both forms having derived certain
special, but nearly equal advantages, from their differently shaped organs.
It is not known that male crustaceans fight together for the possession of
the females, but it is probably the case; for with most animals when the
male is larger than the female, he seems to owe his greater size to his
ancestors having fought with other males during many generations. In most
of the orders, especially in the highest or the Brachyura, the male is
larger than the female; the parasitic genera, however, in which the sexes
follow different habits of life, and most of the Entomostraca must be
excepted. The chelae of many crustaceans are weapons well adapted for
fighting. Thus when a Devil-crab (Portunus puber) was seen by a son of Mr.
Bate fighting with a Carcinus maenas, the latter was soon thrown on its
back, and had every limb torn from its body. When several males of a
Brazilian Gelasimus, a species furnished with immense pincers, were placed
together in a glass vessel by Fritz Muller, they mutilated and killed one
another. Mr. Bate put a large male Carcinus maenas into a pan of water,
inhabited by a female which was paired with a smaller male; but the latter
was soon dispossessed. Mr. Bate adds, "if they fought, the victory was a
bloodless one, for I saw no wounds." This same naturalist separated a male
sand-skipper (so common on our sea-shores), Gammarus marinus, from its
female, both of whom were imprisoned in the same vessel with many
individuals of the same species. The female, when thus divorced, soon
joined the others. After a time the male was put again into the same
vessel; and he then, after swimming about for a time, dashed into the
crowd, and without any fighting at once took away his wife. This fact
shews that in the Amphipoda, an order low in the scale, the males and
females recognise each other, and are mutually attached.
The mental powers of the Crustacea are probably higher than at first sight
appears probable. Any one who tries to catch one of the shore-crabs, so
common on tropical coasts, will perceive how wary and alert they are.
There is a large crab (Birgus latro), found on coral islands, which makes a
thick bed of the picked fibres of the cocoa-nut, at the bottom of a deep
burrow. It feeds on the fallen fruit of this tree by tearing off the husk,
fibre by fibre; and it always begins at that end where the three eye-like
depressions are situated. It then breaks through one of these eyes by
hammering with its heavy front pincers, and turning round, extracts the
albuminous core with its narrow posterior pincers. But these actions are
probably instinctive, so that they would be performed as well by a young
animal as by an old one. The following case, however, can hardly be so
considered: a trustworthy naturalist, Mr. Gardner (14. 'Travels in the
Interior of Brazil,' 1846, p. 111. I have given, in my 'Journal of
Researches,' p. 463, an account of the habits of the Birgus.), whilst
watching a shore-crab (Gelasimus) making its burrow, threw some shells
towards the hole. One rolled in, and three other shells remained within a
few inches of the mouth. In about five minutes the crab brought out the
shell which had fallen in, and carried it away to a distance of a foot; it
then saw the three other shells lying near, and evidently thinking that
they might likewise roll in, carried them to the spot where it had laid the
first. It would, I think, be difficult to distinguish this act from one
performed by man by the aid of reason.
Mr. Bate does not know of any well-marked case of difference of colour in
the two sexes of our British crustaceans, in which respect the sexes of the
higher animals so often differ. In some cases, however, the males and
females differ slightly in tint, but Mr. Bate thinks not more than may be
accounted for by their different habits of life, such as by the male
wandering more about, and being thus more exposed to the light. Dr. Power
tried to distinguish by colour the sexes of the several species which
inhabit the Mauritius, but failed, except with one species of Squilla,
probably S. stylifera, the male of which is described as being "of a
beautiful bluish-green," with some of the appendages cherry-red, whilst the
female is clouded with brown and grey, "with the red about her much less
vivid than in the male." (15. Mr. Ch. Fraser, in 'Proc. Zoolog. Soc.'
1869, p. 3. I am indebted to Mr. Bate for Dr. Power's statement.) In this
case, we may suspect the agency of sexual selection. From M. Bert's
observations on Daphnia, when placed in a vessel illuminated by a prism, we
have reason to believe that even the lowest crustaceans can distinguish
colours. With Saphirina (an oceanic genus of Entomostraca), the males are
furnished with minute shields or cell-like bodies, which exhibit beautiful
changing colours; these are absent in the females, and in both sexes of one
species. (16. Claus, 'Die freilebenden Copepoden,' 1863, s. 35.) It
would, however, be extremely rash to conclude that these curious organs
serve to attract the females. I am informed by Fritz Muller, that in the
female of a Brazilian species of Gelasimus, the whole body is of a nearly
uniform greyish-brown. In the male the posterior part of the cephalo-
thorax is pure white, with the anterior part of a rich green, shading into
dark brown; and it is remarkable that these colours are liable to change in
the course of a few minutes--the white becoming dirty grey or even black,
the green "losing much of its brilliancy." It deserves especial notice
that the males do not acquire their bright colours until they become
mature. They appear to be much more numerous than the females; they differ
also in the larger size of their chelae. In some species of the genus,
probably in all, the sexes pair and inhabit the same burrow. They are
also, as we have seen, highly intelligent animals. From these various
considerations it seems probable that the male in this species has become
gaily ornamented in order to attract or excite the female.
It has just been stated that the male Gelasimus does not acquire his
conspicuous colours until mature and nearly ready to breed. This seems a
general rule in the whole class in respect to the many remarkable
structural differences between the sexes. We shall hereafter find the same
law prevailing throughout the great sub-kingdom of the Vertebrata; and in
all cases it is eminently distinctive of characters which have been
acquired through sexual selection. Fritz Muller (17. 'Facts and
Arguments,' etc., p. 79.) gives some striking instances of this law; thus
the male sand-hopper (Orchestia) does not, until nearly full grown, acquire
his large claspers, which are very differently constructed from those of
the female; whilst young, his claspers resemble those of the female.
CLASS, ARACHNIDA (SPIDERS).
The sexes do not generally differ much in colour, but the males are often
darker than the females, as may be seen in Mr. Blackwall's magnificent
work. (18. 'A History of the Spiders of Great Britain,' 1861-64. For the
following facts, see pp. 77, 88, 102.) In some species, however, the
difference is conspicuous: thus the female of Sparassus smaragdulus is
dullish green, whilst the adult male has the abdomen of a fine yellow, with
three longitudinal stripes of rich red. In certain species of Thomisus the
sexes closely resemble each other, in others they differ much; and
analogous cases occur in many other genera. It is often difficult to say
which of the two sexes departs most from the ordinary coloration of the
genus to which the species belong; but Mr. Blackwall thinks that, as a
general rule, it is the male; and Canestrini (19. This author has recently
published a valuable essay on the 'Caratteri sessuali secondarii degli
Arachnidi,' in the 'Atti della Soc. Veneto-Trentina di Sc. Nat. Padova,'
vol. i. Fasc. 3, 1873.) remarks that in certain genera the males can be
specifically distinguished with ease, but the females with great
difficulty. I am informed by Mr. Blackwall that the sexes whilst young
usually resemble each other; and both often undergo great changes in colour
during their successive moults, before arriving at maturity. In other
cases the male alone appears to change colour. Thus the male of the above
bright-coloured Sparassus at first resembles the female, and acquires his
peculiar tints only when nearly adult. Spiders are possessed of acute
senses, and exhibit much intelligence; as is well known, the females often
shew the strongest affection for their eggs, which they carry about
enveloped in a silken web. The males search eagerly for the females, and
have been seen by Canestrini and others to fight for possession of them.
This same author says that the union of the two sexes has been observed in
about twenty species; and he asserts positively that the female rejects
some of the males who court her, threatens them with open mandibles, and at
last after long hesitation accepts the chosen one. From these several
considerations, we may admit with some confidence that the well-marked
differences in colour between the sexes of certain species are the results
of sexual selection; though we have not here the best kind of evidence,--
the display by the male of his ornaments. From the extreme variability of
colour in the male of some species, for instance of Theridion lineatum, it
would appear that these sexual characters of the males have not as yet
become well fixed. Canestrini draws the same conclusion from the fact that
the males of certain species present two forms, differing from each other
in the size and length of their jaws; and this reminds us of the above
cases of dimorphic crustaceans.
The male is generally much smaller than the female, sometimes to an
extraordinary degree (20. Aug. Vinson ('Araneides des Iles de la Reunion,'
pl. vi. figs. 1 and 2) gives a good instance of the small size of the male,
in Epeira nigra. In this species, as I may add, the male is testaceous and
the female black with legs banded with red. Other even more striking cases
of inequality in size between the sexes have been recorded ('Quarterly
Journal of Science,' July 1868, p. 429); but I have not seen the original
accounts.), and he is forced to be extremely cautious in making his
advances, as the female often carries her coyness to a dangerous pitch. De
Geer saw a male that "in the midst of his preparatory caresses was seized
by the object of his attentions, enveloped by her in a web and then
devoured, a sight which, as he adds, filled him with horror and
indignation." (21. Kirby and Spence, 'Introduction to Entomology,' vol.
i. 1818, p. 280.) The Rev. O.P. Cambridge (22. 'Proceedings, Zoological
Society,' 1871, p. 621.) accounts in the following manner for the extreme
smallness of the male in the genus Nephila. "M. Vinson gives a graphic
account of the agile way in which the diminutive male escapes from the
ferocity of the female, by gliding about and playing hide and seek over her
body and along her gigantic limbs: in such a pursuit it is evident that
the chances of escape would be in favour of the smallest males, while the
larger ones would fall early victims; thus gradually a diminutive race of
males would be selected, until at last they would dwindle to the smallest
possible size compatible with the exercise of their generative functions,--
in fact, probably to the size we now see them, i.e., so small as to be a
sort of parasite upon the female, and either beneath her notice, or too
agile and too small for her to catch without great difficulty."
Westring has made the interesting discovery that the males of several
species of Theridion (23. Theridion (Asagena, Sund.) serratipes, 4-
punctatum et guttatum; see Westring, in Kroyer, 'Naturhist. Tidskrift,'
vol. iv. 1842-1843, p. 349; and vol. ii. 1846-1849, p. 342. See, also, for
other species, 'Araneae Suecicae,' p. 184.) have the power of making a
stridulating sound, whilst the females are mute. The apparatus consists of
a serrated ridge at the base of the abdomen, against which the hard hinder
part of the thorax is rubbed; and of this structure not a trace can be
detected in the females. It deserves notice that several writers,
including the well-known arachnologist Walckenaer, have declared that
spiders are attracted by music. (24. Dr. H.H. van Zouteveen, in his Dutch
translation of this work (vol. i. p. 444), has collected several cases.)
From the analogy of the Orthoptera and Homoptera, to be described in the
next chapter, we may feel almost sure that the stridulation serves, as
Westring also believes, to call or to excite the female; and this is the
first case known to me in the ascending scale of the animal kingdom of
sounds emitted for this purpose. (25. Hilgendorf, however, has lately
called attention to an analogous structure in some of the higher
crustaceans, which seems adapted to produce sound; see 'Zoological Record,'
1869, p. 603.)
CLASS, MYRIAPODA.
In neither of the two orders in this class, the millipedes and centipedes,
can I find any well-marked instances of such sexual differences as more
particularly concern us. In Glomeris limbata, however, and perhaps in some
few other species, the males differ slightly in colour from the females;
but this Glomeris is a highly variable species. In the males of the
Diplopoda, the legs belonging either to one of the anterior or of the
posterior segments of the body are modified into prehensile hooks which
serve to secure the female. In some species of Iulus the tarsi of the male
are furnished with membranous suckers for the same purpose. As we shall
see when we treat of Insects, it is a much more unusual circumstance, that
it is the female in Lithobius, which is furnished with prehensile
appendages at the extremity of her body for holding the male. (26.
Walckenaer et P. Gervais, 'Hist. Nat. des Insectes: Apteres,' tom. iv.
1847, pp. 17, 19, 68.)
CHAPTER X.
SECONDARY SEXUAL CHARACTERS OF INSECTS.
Diversified structures possessed by the males for seizing the females--
Differences between the sexes, of which the meaning is not understood--
Difference in size between the sexes--Thysanura--Diptera--Hemiptera--
Homoptera, musical powers possessed by the males alone--Orthoptera, musical
instruments of the males, much diversified in structure; pugnacity;
colours--Neuroptera, sexual differences in colour--Hymenoptera, pugnacity
and odours--Coleoptera, colours; furnished with great horns, apparently as
an ornament; battles, stridulating organs generally common to both sexes.
In the immense class of insects the sexes sometimes differ in their
locomotive-organs, and often in their sense-organs, as in the pectinated
and beautifully plumose antennae of the males of many species. In Chloeon,
one of the Ephemerae, the male has great pillared eyes, of which the female
is entirely destitute. (1. Sir J. Lubbock, 'Transact. Linnean Soc.' vol.
xxv, 1866, p. 484. With respect to the Mutillidae see Westwood, 'Modern
Class. of Insects,' vol. ii. p. 213.) The ocelli are absent in the females
of certain insects, as in the Mutillidae; and here the females are likewise
wingless. But we are chiefly concerned with structures by which one male
is enabled to conquer another, either in battle or courtship, through his
strength, pugnacity, ornaments, or music. The innumerable contrivances,
therefore, by which the male is able to seize the female, may be briefly
passed over. Besides the complex structures at the apex of the abdomen,
which ought perhaps to be ranked as primary organs (2. These organs in the
male often differ in closely-allied species, and afford excellent specific
characters. But their importance, from a functional point of view, as Mr.
R. MacLachlan has remarked to me, has probably been overrated. It has been
suggested, that slight differences in these organs would suffice to prevent
the intercrossing of well-marked varieties or incipient species, and would
thus aid in their development. That this can hardly be the case, we may
infer from the many recorded cases (see, for instance, Bronn, 'Geschichte
der Natur,' B. ii. 1843, s. 164; and Westwood, 'Transact. Ent. Soc.' vol.
iii. 1842, p. 195) of distinct species having been observed in union. Mr.
MacLachlan informs me (vide 'Stett. Ent. Zeitung,' 1867, s. 155) that when
several species of Phryganidae, which present strongly-pronounced
differences of this kind, were confined together by Dr. Aug. Meyer, THEY
COUPLED, and one pair produced fertile ova.), "it is astonishing," as Mr.
B.D. Walsh (3. 'The Practical Entomologist,' Philadelphia, vol. ii. May
1867, p 88.) has remarked, "how many different organs are worked in by
nature for the seemingly insignificant object of enabling the male to grasp
the female firmly." The mandibles or jaws are sometimes used for this
purpose; thus the male Corydalis cornutus (a neuropterous insect in some
degree allied to the Dragon flies, etc.) has immense curved jaws, many
times longer than those of the female; and they are smooth instead of being
toothed, so that he is thus enabled to seize her without injury. (4. Mr.
Walsh, ibid. p. 107.) One of the stag-beetles of North America (Lucanus
elaphus) uses his jaws, which are much larger than those of the female, for
the same purpose, but probably likewise for fighting. In one of the sand-
wasps (Ammophila) the jaws in the two sexes are closely alike, but are used
for widely different purposes: the males, as Professor Westwood observes,
"are exceedingly ardent, seizing their partners round the neck with their
sickle-shaped jaws" (5. 'Modern Classification of Insects,' vol. ii. 1840,
pp. 205, 206. Mr. Walsh, who called my attention to the double use of the
jaws, says that he has repeatedly observed this fact.); whilst the females
use these organs for burrowing in sand-banks and making their nests.
[Fig. 9. Crabro cribrarius. Upper figure, male; lower figure, female.]
The tarsi of the front-legs are dilated in many male beetles, or are
furnished with broad cushions of hairs; and in many genera of water-beetles
they are armed with a round flat sucker, so that the male may adhere to the
slippery body of the female. It is a much more unusual circumstance that
the females of some water-beetles (Dytiscus) have their elytra deeply
grooved, and in Acilius sulcatus thickly set with hairs, as an aid to the
male. The females of some other water-beetles (Hydroporus) have their
elytra punctured for the same purpose. (6. We have here a curious and
inexplicable case of dimorphism, for some of the females of four European
species of Dytiscus, and of certain species of Hydroporus, have their
elytra smooth; and no intermediate gradations between the sulcated or
punctured, and the quite smooth elytra have been observed. See Dr. H.
Schaum, as quoted in the 'Zoologist,' vols. v.-vi. 1847-48, p. 1896. Also
Kirby and Spence, 'Introduction to Entomology,' vol. iii. 1826, p. 305.)
In the male of Crabro cribrarius (Fig. 9), it is the tibia which is dilated
into a broad horny plate, with minute membraneous dots, giving to it a
singular appearance like that of a riddle. (7. Westwood, 'Modern Class.'
vol. ii. p. 193. The following statement about Penthe, and others in
inverted commas, are taken from Mr. Walsh, 'Practical Entomologist,'
Philadelphia, vol. iii. p. 88.) In the male of Penthe (a genus of beetles)
a few of the middle joints of the antennae are dilated and furnished on the
inferior surface with cushions of hair, exactly like those on the tarsi of
the Carabidae, "and obviously for the same end." In male dragon-flies,
"the appendages at the tip of the tail are modified in an almost infinite
variety of curious patterns to enable them to embrace the neck of the
female." Lastly, in the males of many insects, the legs are furnished with
peculiar spines, knobs or spurs; or the whole leg is bowed or thickened,
but this is by no means invariably a sexual character; or one pair, or all
three pairs are elongated, sometimes to an extravagant length. (8. Kirby
and Spence, 'Introduct.' etc., vol. iii. pp. 332-336.)
[Fig. 10. Taphroderes distortus (much enlarged). Upper figure, male;
lower figure, female.]
The sexes of many species in all the orders present differences, of which
the meaning is not understood. One curious case is that of a beetle (Fig.
10), the male of which has left mandible much enlarged; so that the mouth
is greatly distorted. In another Carabidous beetle, Eurygnathus (9.
'Insecta Maderensia,' 1854, page 20.), we have the case, unique as far as
known to Mr. Wollaston, of the head of the female being much broader and
larger, though in a variable degree, than that of the male. Any number of
such cases could be given. They abound in the Lepidoptera: one of the
most extraordinary is that certain male butterflies have their fore-legs
more or less atrophied, with the tibiae and tarsi reduced to mere
rudimentary knobs. The wings, also, in the two sexes often differ in
neuration (10. E. Doubleday, 'Annals and Mag. of Nat. Hist.' vol. i. 1848,
p. 379. I may add that the wings in certain Hymenoptera (see Shuckard,
'Fossorial Hymenoptera,' 1837, pp. 39-43) differ in neuration according to
sex.), and sometimes considerably in outline, as in the Aricoris epitus,
which was shewn to me in the British Museum by Mr. A. Butler. The males of
certain South American butterflies have tufts of hair on the margins of the
wings, and horny excrescences on the discs of the posterior pair. (11.
H.W. Bates, in 'Journal of Proc. Linn. Soc.' vol. vi. 1862, p. 74. Mr.
Wonfor's observations are quoted in 'Popular Science Review,' 1868, p.
343.) In several British butterflies, as shewn by Mr. Wonfor, the males
alone are in parts clothed with peculiar scales.
The use of the bright light of the female glow-worm has been subject to
much discussion. The male is feebly luminous, as are the larvae and even
the eggs. It has been supposed by some authors that the light serves to
frighten away enemies, and by others to guide the male to the female. At
last, Mr. Belt (12. 'The Naturalist in Nicaragua,' 1874, pp. 316-320. On
the phosphorescence of the eggs, see 'Annals and Magazine of Natural
History,' Nov. 1871, p. 372.) appears to have solved the difficulty: he
finds that all the Lampyridae which he has tried are highly distasteful to
insectivorous mammals and birds. Hence it is in accordance with Mr. Bates'
view, hereafter to be explained, that many insects mimic the Lampyridae
closely, in order to be mistaken for them, and thus to escape destruction.
He further believes that the luminous species profit by being at once
recognised as unpalatable. It is probable that the same explanation may be
extended to the Elaters, both sexes of which are highly luminous. It is
not known why the wings of the female glow-worm have not been developed;
but in her present state she closely resembles a larva, and as larvae are
so largely preyed on by many animals, we can understand why she has been
rendered so much more luminous and conspicuous than the male; and why the
larvae themselves are likewise luminous.
DIFFERENCE IN SIZE BETWEEN THE SEXES.
With insects of all kinds the males are commonly smaller than the females;
and this difference can often be detected even in the larval state. So
considerable is the difference between the male and female cocoons of the
silk-moth (Bombyx mori), that in France they are separated by a particular
mode of weighing. (13. Robinet, 'Vers a Soie,' 1848, p. 207.) In the
lower classes of the animal kingdom, the greater size of the females seems
generally to depend on their developing an enormous number of ova; and this
may to a certain extent hold good with insects. But Dr. Wallace has
suggested a much more probable explanation. He finds, after carefully
attending to the development of the caterpillars of Bombyx cynthia and
yamamai, and especially to that of some dwarfed caterpillars reared from a
second brood on unnatural food, "that in proportion as the individual moth
is finer, so is the time required for its metamorphosis longer; and for
this reason the female, which is the larger and heavier insect, from having
to carry her numerous eggs, will be preceded by the male, which is smaller
and has less to mature." (14. 'Transact. Ent. Soc.' 3rd series, vol. v.
p. 486.) Now as most insects are short-lived, and as they are exposed to
many dangers, it would manifestly be advantageous to the female to be
impregnated as soon as possible. This end would be gained by the males
being first matured in large numbers ready for the advent of the females;
and this again would naturally follow, as Mr. A.R. Wallace has remarked
(15. 'Journal of Proc. Ent. Soc.' Feb. 4, 1867, p. lxxi.), through natural
selection; for the smaller males would be first matured, and thus would
procreate a large number of offspring which would inherit the reduced size
of their male parents, whilst the larger males from being matured later
would leave fewer offspring.
There are, however, exceptions to the rule of male insects being smaller
than the females: and some of these exceptions are intelligible. Size and
strength would be an advantage to the males, which fight for the possession
of the females; and in these cases, as with the stag-beetle (Lucanus), the
males are larger than the females. There are, however, other beetles which
are not known to fight together, of which the males exceed the females in
size; and the meaning of this fact is not known; but in some of these
cases, as with the huge Dynastes and Megasoma, we can at least see that
there would be no necessity for the males to be smaller than the females,
in order to be matured before them, for these beetles are not short-lived,
and there would be ample time for the pairing of the sexes. So again, male
dragon-flies (Libellulidae) are sometimes sensibly larger, and never
smaller, than the females (16. For this and other statements on the size
of the sexes, see Kirby and Spence, ibid. vol. iii. p. 300; on the duration
of life in insects, see p. 344.); and as Mr. MacLachlan believes, they do
not generally pair with the females until a week or fortnight has elapsed,
and until they have assumed their proper masculine colours. But the most
curious case, shewing on what complex and easily-overlooked relations, so
trifling a character as difference in size between the sexes may depend, is
that of the aculeate Hymenoptera; for Mr. F. Smith informs me that
throughout nearly the whole of this large group, the males, in accordance
with the general rule, are smaller than the females, and emerge about a
week before them; but amongst the Bees, the males of Apis mellifica,
Anthidium manicatum, and Anthophora acervorum, and amongst the Fossores,
the males of the Methoca ichneumonides, are larger than the females. The
explanation of this anomaly is that a marriage flight is absolutely
necessary with these species, and the male requires great strength and size
in order to carry the female through the air. Increased size has here been
acquired in opposition to the usual relation between size and the period of
development, for the males, though larger, emerge before the smaller
females.
We will now review the several Orders, selecting such facts as more
particularly concern us. The Lepidoptera (Butterflies and Moths) will be
retained for a separate chapter.
ORDER, THYSANURA.
The members of this lowly organised order are wingless, dull-coloured,
minute insects, with ugly, almost misshapen heads and bodies. Their sexes
do not differ, but they are interesting as shewing us that the males pay
sedulous court to the females even low down in the animal scale. Sir J.
Lubbock (17. 'Transact. Linnean Soc.' vol. xxvi. 1868, p. 296.) says: "it
is very amusing to see these little creatures (Smynthurus luteus)
coquetting together. The male, which is much smaller than the female, runs
round her, and they butt one another, standing face to face and moving
backward and forward like two playful lambs. Then the female pretends to
run away and the male runs after her with a queer appearance of anger, gets
in front and stands facing her again; then she turns coyly round, but he,
quicker and more active, scuttles round too, and seems to whip her with his
antennae; then for a bit they stand face to face, play with their antennae,
and seem to be all in all to one another."
ORDER, DIPTERA (FLIES).
The sexes differ little in colour. The greatest difference, known to Mr.
F. Walker, is in the genus Bibio, in which the males are blackish or quite
black, and the females obscure brownish-orange. The genus Elaphomyia,
discovered by Mr. Wallace (18. 'The Malay Archipelago,' vol. ii. 1869, p.
313.) in New Guinea, is highly remarkable, as the males are furnished with
horns, of which the females are quite destitute. The horns spring from
beneath the eyes, and curiously resemble those of a stag, being either
branched or palmated. In one of the species, they equal the whole body in
length. They might be thought to be adapted for fighting, but as in one
species they are of a beautiful pink colour, edged with black, with a pale
central stripe, and as these insects have altogether a very elegant
appearance, it is perhaps more probable that they serve as ornaments. That
the males of some Diptera fight together is certain; Prof. Westwood (19.
'Modern Classification of Insects,' vol. ii. 1840, p. 526.) has several
times seen this with the Tipulae. The males of other Diptera apparently
try to win the females by their music: H. Muller (20. 'Anwendung,' etc.,
'Verh. d. n. V. Jahrg.' xxix. p. 80. Mayer, in 'American Naturalist,'
1874, p. 236.) watched for some time two males of an Eristalis courting a
female; they hovered above her, and flew from side to side, making a high
humming noise at the same time. Gnats and mosquitoes (Culicidae) also seem
to attract each other by humming; and Prof. Mayer has recently ascertained
that the hairs on the antennae of the male vibrate in unison with the notes
of a tuning-fork, within the range of the sounds emitted by the female.
The longer hairs vibrate sympathetically with the graver notes, and the
shorter hairs with the higher ones. Landois also asserts that he has
repeatedly drawn down a whole swarm of gnats by uttering a particular note.
It may be added that the mental faculties of the Diptera are probably
higher than in most other insects, in accordance with their highly-
developed nervous system. (21. See Mr. B.T. Lowne's interesting work, 'On
the Anatomy of the Blow-fly, Musca vomitoria,' 1870, p. 14. He remarks (p.
33) that, "the captured flies utter a peculiar plaintive note, and that
this sound causes other flies to disappear.")
ORDER, HEMIPTERA (FIELD-BUGS).
Mr. J.W. Douglas, who has particularly attended to the British species, has
kindly given me an account of their sexual differences. The males of some
species are furnished with wings, whilst the females are wingless; the
sexes differ in the form of their bodies, elytra, antennae and tarsi; but
as the signification of these differences are unknown, they may be here
passed over. The females are generally larger and more robust than the
males. With British, and, as far as Mr. Douglas knows, with exotic
species, the sexes do not commonly differ much in colour; but in about six
British species the male is considerably darker than the female, and in
about four other species the female is darker than the male. Both sexes of
some species are beautifully coloured; and as these insects emit an
extremely nauseous odour, their conspicuous colours may serve as a signal
that they are unpalatable to insectivorous animals. In some few cases
their colours appear to be directly protective: thus Prof. Hoffmann
informs me that he could hardly distinguish a small pink and green species
from the buds on the trunks of lime-trees, which this insect frequents.
Some species of Reduvidae make a stridulating noise; and, in the case of
Pirates stridulus, this is said (22. Westwood, 'Modern Classification of
Insects,' vol. ii. p. 473.) to be effected by the movement of the neck
within the pro-thoracic cavity. According to Westring, Reduvius personatus
also stridulates. But I have no reason to suppose that this is a sexual
character, excepting that with non-social insects there seems to be no use
for sound-producing organs, unless it be as a sexual call.
ORDER: HOMOPTERA.
Every one who has wandered in a tropical forest must have been astonished
at the din made by the male Cicadae. The females are mute; as the Grecian
poet Xenarchus says, "Happy the Cicadas live, since they all have voiceless
wives." The noise thus made could be plainly heard on board the "Beagle,"
when anchored at a quarter of a mile from the shore of Brazil; and Captain
Hancock says it can be heard at the distance of a mile. The Greeks
formerly kept, and the Chinese now keep these insects in cages for the sake
of their song, so that it must be pleasing to the ears of some men. (23.
These particulars are taken from Westwood's 'Modern Classification of
Insects,' vol. ii. 1840, p. 422. See, also, on the Fulgoridae, Kirby and
Spence, 'Introduct.' vol. ii. p. 401.) The Cicadidae usually sing during
the day, whilst the Fulgoridae appear to be night-songsters. The sound,
according to Landois (24. 'Zeitschrift fur wissenschaft Zoolog.' B. xvii.
1867, ss. 152-158.), is produced by the vibration of the lips of the
spiracles, which are set into motion by a current of air emitted from the
tracheae; but this view has lately been disputed. Dr. Powell appears to
have proved (25. 'Transactions of the New Zealand Institute,' vol. v.
1873, p. 286.) that it is produced by the vibration of a membrane, set into
action by a special muscle. In the living insect, whilst stridulating,
this membrane can be seen to vibrate; and in the dead insect the proper
sound is heard, if the muscle, when a little dried and hardened, is pulled
with the point of a pin. In the female the whole complex musical apparatus
is present, but is much less developed than in the male, and is never used
for producing sound.
With respect to the object of the music, Dr. Hartman, in speaking of the
Cicada septemdecim of the United States, says (26. I am indebted to Mr.
Walsh for having sent me this extract from 'A Journal of the Doings of
Cicada septemdecim,' by Dr. Hartman.), "the drums are now (June 6th and
7th, 1851) heard in all directions. This I believe to be the marital
summons from the males. Standing in thick chestnut sprouts about as high
as my head, where hundreds were around me, I observed the females coming
around the drumming males." He adds, "this season (Aug. 1868) a dwarf
pear-tree in my garden produced about fifty larvae of Cic. pruinosa; and I
several times noticed the females to alight near a male while he was
uttering his clanging notes." Fritz Muller writes to me from S. Brazil
that he has often listened to a musical contest between two or three males
of a species with a particularly loud voice, seated at a considerable
distance from each other: as soon as one had finished his song, another
immediately began, and then another. As there is so much rivalry between
the males, it is probable that the females not only find them by their
sounds, but that, like female birds, they are excited or allured by the
male with the most attractive voice.
I have not heard of any well-marked cases of ornamental differences between
the sexes of the Homoptera. Mr. Douglas informs me that there are three
British species, in which the male is black or marked with black bands,
whilst the females are pale-coloured or obscure.
ORDER, ORTHOPTERA (CRICKETS AND GRASSHOPPERS).
The males in the three saltatorial families in this Order are remarkable
for their musical powers, namely the Achetidae or crickets, the Locustidae
for which there is no equivalent English name, and the Acridiidae or
grasshoppers. The stridulation produced by some of the Locustidae is so
loud that it can be heard during the night at the distance of a mile (27.
L. Guilding, 'Transactions of the Linnean Society,' vol. xv. p. 154.); and
that made by certain species is not unmusical even to the human ear, so
that the Indians on the Amazons keep them in wicker cages. All observers
agree that the sounds serve either to call or excite the mute females.
With respect to the migratory locusts of Russia, Korte has given (28. I
state this on the authority of Koppen, 'Uber die Heuschrecken in
Sudrussland,' 1866, p. 32, for I have in vain endeavoured to procure
Korte's work.) an interesting case of selection by the female of a male.
The males of this species (Pachytylus migratorius) whilst coupled with the
female stridulate from anger or jealousy, if approached by other males.
The house-cricket when surprised at night uses its voice to warn its
fellows. (29. Gilbert White, 'Natural History of Selborne,' vol. ii.
1825, p. 262.) In North America the Katy-did (Platyphyllum concavum, one
of the Locustidae) is described (30. Harris, 'Insects of New England,'
1842, p. 128.) as mounting on the upper branches of a tree, and in the
evening beginning "his noisy babble, while rival notes issue from the
neighbouring trees, and the groves resound with the call of Katy-did-she-
did the live-long night." Mr. Bates, in speaking of the European field-
cricket (one of the Achetidae), says "the male has been observed to place
himself in the evening at the entrance of his burrow, and stridulate until
a female approaches, when the louder notes are succeeded by a more subdued
tone, whilst the successful musician caresses with his antennae the mate he
has won." (31. 'The Naturalist on the Amazons,' vol. i. 1863, p. 252. Mr.
Bates gives a very interesting discussion on the gradations in the musical
apparatus of the three families. See also Westwood, 'Modern Classification
of Insects,' vol. ii. pp. 445 and 453.) Dr. Scudder was able to excite one
of these insects to answer him, by rubbing on a file with a quill. (32.
'Proceedings of the Boston Society of Natural History,' vol. xi. April
1868.) In both sexes a remarkable auditory apparatus has been discovered
by Von Siebold, situated in the front legs. (33. 'Nouveau Manuel d'Anat.
Comp.' (French translat.), tom. 1, 1850, p. 567.)
[Fig.11. Gryllus campestris (from Landois).
Right-hand figure, under side of part of a wing-nervure, much magnified,
showing the teeth, st.
Left-hand figure, upper surface of wing-cover, with the projecting, smooth
nervure, r, across which the teeth (st) are scraped.
Fig.12. Teeth of Nervure of Gryllus domesticus (from Landois).]
In the three Families the sounds are differently produced. In the males of
the Achetidae both wing-covers have the same apparatus; and this in the
field-cricket (see Gryllus campestris, Fig. 11) consists, as described by
Landois (34. 'Zeitschrift fur wissenschaft. Zoolog.' B. xvii. 1867, s.
117.), of from 131 to 138 sharp, transverse ridges or teeth (st) on the
under side of one of the nervures of the wing-cover. This toothed nervure
is rapidly scraped across a projecting, smooth, hard nervure (r) on the
upper surface of the opposite wing. First one wing is rubbed over the
other, and then the movement is reversed. Both wings are raised a little
at the same time, so as to increase the resonance. In some species the
wing-covers of the males are furnished at the base with a talc-like plate.
(35. Westwood, 'Modern Classification of Insects,' vol. i. p. 440.) I
here give a drawing (Fig. 12) of the teeth on the under side of the nervure
of another species of Gryllus, viz., G. domesticus. With respect to the
formation of these teeth, Dr. Gruber has shewn (36. 'Ueber der Tonapparat
der Locustiden, ein Beitrag zum Darwinismus,' 'Zeitschrift fur
wissenschaft. Zoolog.' B. xxii. 1872, p. 100.) that they have been
developed by the aid of selection, from the minute scales and hairs with
which the wings and body are covered, and I came to the same conclusion
with respect to those of the Coleoptera. But Dr. Gruber further shews that
their development is in part directly due to the stimulus from the friction
of one wing over the other.
[Fig.13. Chlorocoelus Tanana (from Bates).
a,b. Lobes of opposite wing-covers.]
In the Locustidae the opposite wing-covers differ from each other in
structure (Fig. 13), and the action cannot, as in the last family, be
reversed. The left wing, which acts as the bow, lies over the right wing
which serves as the fiddle. One of the nervures (a) on the under surface
of the former is finely serrated, and is scraped across the prominent
nervures on the upper surface of the opposite or right wing. In our
British Phasgonura viridissima it appeared to me that the serrated nervure
is rubbed against the rounded hind-corner of the opposite wing, the edge of
which is thickened, coloured brown, and very sharp. In the right wing, but
not in the left, there is a little plate, as transparent as talc,
surrounded by nervures, and called the speculum. In Ephippiger vitium, a
member of this same family, we have a curious subordinate modification; for
the wing-covers are greatly reduced in size, but "the posterior part of the
pro-thorax is elevated into a kind of dome over the wing-covers, and which
has probably the effect of increasing the sound." (37. Westwood 'Modern
Classification of Insects,' vol. i. p. 453.)
We thus see that the musical apparatus is more differentiated or
specialised in the Locustidae (which include, I believe, the most powerful
performers in the Order), than in the Achetidae, in which both wing-covers
have the same structure and the same function. (38. Landois, 'Zeitschrift
fur wissenschaft Zoolog.' B. xvii. 1867, ss. 121, 122.) Landois, however,
detected in one of the Locustidae, namely in Decticus, a short and narrow
row of small teeth, mere rudiments, on the inferior surface of the right
wing-cover, which underlies the other and is never used as the bow. I
observed the same rudimentary structure on the under side of the right
wing-cover in Phasgonura viridissima. Hence we may infer with confidence
that the Locustidae are descended from a form, in which, as in the existing
Achetidae, both wing-covers had serrated nervures on the under surface, and
could be indifferently used as the bow; but that in the Locustidae the two
wing-covers gradually became differentiated and perfected, on the principle
of the division of labour, the one to act exclusively as the bow, and the
other as the fiddle. Dr. Gruber takes the same view, and has shewn that
rudimentary teeth are commonly found on the inferior surface of the right
wing. By what steps the more simple apparatus in the Achetidae originated,
we do not know, but it is probable that the basal portions of the wing-
covers originally overlapped each other as they do at present; and that the
friction of the nervures produced a grating sound, as is now the case with
the wing-covers of the females. (39. Mr. Walsh also informs me that he
has noticed that the female of the Platyphyllum concavum, "when captured
makes a feeble grating noise by shuffling her wing-covers together.") A
grating sound thus occasionally and accidentally made by the males, if it
served them ever so little as a love-call to the females, might readily
have been intensified through sexual selection, by variations in the
roughness of the nervures having been continually preserved.
[Fig.14. Hind-leg of Stenobothrus pratorum:
r, the stridulating ridge;
lower figure, the teeth forming the ridge, much magnified (from Landois).
Fig.15. Pneumora (from specimens in the British Museum).
Upper figure, male;
lower figure, female.]
In the last and third family, namely the Acridiidae or grasshoppers, the
stridulation is produced in a very different manner, and according to Dr.
Scudder, is not so shrill as in the preceding Families. The inner surface
of the femur (Fig. 14, r) is furnished with a longitudinal row of minute,
elegant, lancet-shaped, elastic teeth, from 85 to 93 in number (40.
Landois, ibid. s. 113.); and these are scraped across the sharp, projecting
nervures on the wing-covers, which are thus made to vibrate and resound.
Harris (41. 'Insects of New England,' 1842, p. 133.) says that when one of
the males begins to play, he first "bends the shank of the hind-leg beneath
the thigh, where it is lodged in a furrow designed to receive it, and then
draws the leg briskly up and down. He does not play both fiddles together,
but alternately, first upon one and then on the other." In many species,
the base of the abdomen is hollowed out into a great cavity which is
believed to act as a resounding board. In Pneumora (Fig. 15), a S. African
genus belonging to the same family, we meet with a new and remarkable
modification; in the males a small notched ridge projects obliquely from
each side of the abdomen, against which the hind femora are rubbed. (42.
Westwood, 'Modern Classification,' vol i. p. 462.) As the male is
furnished with wings (the female being wingless), it is remarkable that the
thighs are not rubbed in the usual manner against the wing-covers; but this
may perhaps be accounted for by the unusually small size of the hind-legs.
I have not been able to examine the inner surface of the thighs, which,
judging from analogy, would be finely serrated. The species of Pneumora
have been more profoundly modified for the sake of stridulation than any
other orthopterous insect; for in the male the whole body has been
converted into a musical instrument, being distended with air, like a great
pellucid bladder, so as to increase the resonance. Mr. Trimen informs me
that at the Cape of Good Hope these insects make a wonderful noise during
the night.
In the three foregoing families, the females are almost always destitute of
an efficient musical apparatus. But there are a few exceptions to this
rule, for Dr. Gruber has shewn that both sexes of Ephippiger vitium are
thus provided; though the organs differ in the male and female to a certain
extent. Hence we cannot suppose that they have been transferred from the
male to the female, as appears to have been the case with the secondary
sexual characters of many other animals. They must have been independently
developed in the two sexes, which no doubt mutually call to each other
during the season of love. In most other Locustidae (but not according to
Landois in Decticus) the females have rudiments of the stridulatory organs
proper to the male; from whom it is probable that these have been
transferred. Landois also found such rudiments on the under surface of the
wing-covers of the female Achetidae, and on the femora of the female
Acridiidae. In the Homoptera, also, the females have the proper musical
apparatus in a functionless state; and we shall hereafter meet in other
divisions of the animal kingdom with many instances of structures proper to
the male being present in a rudimentary condition of the female.
Landois has observed another important fact, namely, that in the females of
the Acridiidae, the stridulating teeth on the femora remain throughout life
in the same condition in which they first appear during the larval state in
both sexes. In the males, on the other hand, they become further
developed, and acquire their perfect structure at the last moult, when the
insect is mature and ready to breed.
From the facts now given, we see that the means by which the males of the
Orthoptera produce their sounds are extremely diversified, and are
altogether different from those employed by the Homoptera. (43. Landois
has recently found in certain Orthoptera rudimentary structures closely
similar to the sound-producing organs in the Homoptera; and this is a
surprising fact. See 'Zeitschrift fur wissenschaft Zoolog.' B. xxii. Heft
3, 1871, p. 348.) But throughout the animal kingdom we often find the same
object gained by the most diversified means; this seems due to the whole
organisation having undergone multifarious changes in the course of ages,
and as part after part varied different variations were taken advantage of
for the same general purpose. The diversity of means for producing sound
in the three families of the Orthoptera and in the Homoptera, impresses the
mind with the high importance of these structures to the males, for the
sake of calling or alluring the females. We need feel no surprise at the
amount of modification which the Orthoptera have undergone in this respect,
as we now know, from Dr. Scudder's remarkable discovery (44.
'Transactions, Entomological Society,' 3rd series, vol. ii. ('Journal of
Proceedings,' p. 117).), that there has been more than ample time. This
naturalist has lately found a fossil insect in the Devonian formation of
New Brunswick, which is furnished with "the well-known tympanum or
stridulating apparatus of the male Locustidae." The insect, though in most
respects related to the Neuroptera, appears, as is so often the case with
very ancient forms, to connect the two related Orders of the Neuroptera and
Orthoptera.
I have but little more to say on the Orthoptera. Some of the species are
very pugnacious: when two male field-crickets (Gryllus campestris) are
confined together, they fight till one kills the other; and the species of
Mantis are described as manoeuvring with their sword-like front-limbs, like
hussars with their sabres. The Chinese keep these insects in little bamboo
cages, and match them like game-cocks. (45. Westwood, 'Modern
Classification of Insects,' vol. i. p. 427; for crickets, p. 445.) With
respect to colour, some exotic locusts are beautifully ornamented; the
posterior wings being marked with red, blue, and black; but as throughout
the Order the sexes rarely differ much in colour, it is not probable that
they owe their bright tints to sexual selection. Conspicuous colours may
be of use to these insects, by giving notice that they are unpalatable.
Thus it has been observed (46. Mr. Ch. Horne, in 'Proceedings of the
Entomological Society,' May 3, 1869, p. xii.) that a bright-coloured Indian
locust was invariably rejected when offered to birds and lizards. Some
cases, however, are known of sexual differences in colour in this Order.
The male of an American cricket (47. The Oecanthus nivalis, Harris,
'Insects of New England,' 1842, p. 124. The two sexes of OE. pellucidus of
Europe differ, as I hear from Victor Carus, in nearly the same manner.) is
described as being as white as ivory, whilst the female varies from almost
white to greenish-yellow or dusky. Mr. Walsh informs me that the adult
male of Spectrum femoratum (one of the Phasmidae) "is of a shining
brownish-yellow colour; the adult female being of a dull, opaque, cinereous
brown; the young of both sexes being green." Lastly, I may mention that
the male of one curious kind of cricket (48. Platyblemnus: Westwood,
'Modern Classification,' vol. i. p. 447.) is furnished with "a long
membranous appendage, which falls over the face like a veil;" but what its
use may be, is not known.
ORDER, NEUROPTERA.
Little need here be said, except as to colour. In the Ephemeridae the
sexes often differ slightly in their obscure tints (49. B.D. Walsh, the
'Pseudo-neuroptera of Illinois,' in 'Proceedings of the Entomological
Society of Philadelphia,' 1862, p. 361.); but it is not probable that the
males are thus rendered attractive to the females. The Libellulidae, or
dragon-flies, are ornamented with splendid green, blue, yellow, and
vermilion metallic tints; and the sexes often differ. Thus, as Prof.
Westwood remarks (50. 'Modern Classification,' vol. ii. p. 37.), the males
of some of the Agrionidae, "are of a rich blue with black wings, whilst the
females are fine green with colourless wings." But in Agrion Ramburii
these colours are exactly reversed in the two sexes. (51. Walsh, ibid. p.
381. I am indebted to this naturalist for the following facts on
Hetaerina, Anax, and Gomphus.) In the extensive N. American genus of
Hetaerina, the males alone have a beautiful carmine spot at the base of
each wing. In Anax junius the basal part of the abdomen in the male is a
vivid ultramarine blue, and in the female grass-green. In the allied genus
Gomphus, on the other hand, and in some other genera, the sexes differ but
little in colour. In closely-allied forms throughout the animal kingdom,
similar cases of the sexes differing greatly, or very little, or not at
all, are of frequent occurrence. Although there is so wide a difference in
colour between the sexes of many Libellulidae, it is often difficult to say
which is the more brilliant; and the ordinary coloration of the two sexes
is reversed, as we have just seen, in one species of Agrion. It is not
probable that their colours in any case have been gained as a protection.
Mr. MacLachlan, who has closely attended to this family, writes to me that
dragon-flies--the tyrants of the insect-world--are the least liable of any
insect to be attacked by birds or other enemies, and he believes that their
bright colours serve as a sexual attraction. Certain dragon-flies
apparently are attracted by particular colours: Mr. Patterson observed
(52. 'Transactions, Ent. Soc.' vol. i. 1836, p. lxxxi.) that the
Agrionidae, of which the males are blue, settled in numbers on the blue
float of a fishing line; whilst two other species were attracted by shining
white colours.
It is an interesting fact, first noticed by Schelver, that, in several
genera belonging to two sub-families, the males on first emergence from the
pupal state, are coloured exactly like the females; but that their bodies
in a short time assume a conspicuous milky-blue tint, owing to the
exudation of a kind of oil, soluble in ether and alcohol. Mr. MacLachlan
believes that in the male of Libellula depressa this change of colour does
not occur until nearly a fortnight after the metamorphosis, when the sexes
are ready to pair.
Certain species of Neurothemis present, according to Brauer (53. See
abstract in the 'Zoological Record' for 1867, p. 450.), a curious case of
dimorphism, some of the females having ordinary wings, whilst others have
them "very richly netted, as in the males of the same species." Brauer
"explains the phenomenon on Darwinian principles by the supposition that
the close netting of the veins is a secondary sexual character in the
males, which has been abruptly transferred to some of the females, instead
of, as generally occurs, to all of them." Mr. MacLachlan informs me of
another instance of dimorphism in several species of Agrion, in which some
individuals are of an orange colour, and these are invariably females.
This is probably a case of reversion; for in the true Libellulae, when the
sexes differ in colour, the females are orange or yellow; so that supposing
Agrion to be descended from some primordial form which resembled the
typical Libellulae in its sexual characters, it would not be surprising
that a tendency to vary in this manner should occur in the females alone.
Although many dragon-flies are large, powerful, and fierce insects, the
males have not been observed by Mr. MacLachlan to fight together,
excepting, as he believes, in some of the smaller species of Agrion. In
another group in this Order, namely, the Termites or white ants, both sexes
at the time of swarming may be seen running about, "the male after the
female, sometimes two chasing one female, and contending with great
eagerness who shall win the prize." (54. Kirby and Spence, 'Introduction
to Entomology,' vol. ii. 1818, p. 35.) The Atropos pulsatorius is said to
make a noise with its jaws, which is answered by other individuals. (55.
Houzeau, 'Les Facultes Mentales,' etc. Tom. i. p. 104.)
ORDER, HYMENOPTERA.
That inimitable observer, M. Fabre (56. See an interesting article, 'The
Writings of Fabre,' in 'Nat. Hist. Review,' April 1862, p. 122.), in
describing the habits of Cerceris, a wasp-like insect, remarks that "fights
frequently ensue between the males for the possession of some particular
female, who sits an apparently unconcerned beholder of the struggle for
supremacy, and when the victory is decided, quietly flies away in company
with the conqueror." Westwood (57. 'Journal of Proceedings of
Entomological Society,' Sept. 7, 1863, p. 169.) says that the males of one
of the saw-flies (Tenthredinae) "have been found fighting together, with
their mandibles locked." As M. Fabre speaks of the males of Cerceris
striving to obtain a particular female, it may be well to bear in mind that
insects belonging to this Order have the power of recognising each other
after long intervals of time, and are deeply attached. For instance,
Pierre Huber, whose accuracy no one doubts, separated some ants, and when,
after an interval of four months, they met others which had formerly
belonged to the same community, they recognised and caressed one another
with their antennae. Had they been strangers they would have fought
together. Again, when two communities engage in a battle, the ants on the
same side sometimes attack each other in the general confusion, but they
soon perceive their mistake, and the one ant soothes the other. (58. P.
Huber, 'Recherches sur les Moeurs des Fourmis,' 1810, pp. 150, 165.)
In this Order slight differences in colour, according to sex, are common,
but conspicuous differences are rare except in the family of Bees; yet both
sexes of certain groups are so brilliantly coloured--for instance in
Chrysis, in which vermilion and metallic greens prevail--that we are
tempted to attribute the result to sexual selection. In the Ichneumonidae,
according to Mr. Walsh (59. 'Proceedings of the Entomological Society of
Philadelphia,' 1866, pp. 238, 239.), the males are almost universally
lighter-coloured than the females. On the other hand, in the
Tenthredinidae the males are generally darker than the females. In the
Siricidae the sexes frequently differ; thus the male of Sirex juvencus is
banded with orange, whilst the female is dark purple; but it is difficult
to say which sex is the more ornamented. In Tremex columbae the female is
much brighter coloured than the male. I am informed by Mr. F. Smith, that
the male ants of several species are black, the females being testaceous.
In the family of Bees, especially in the solitary species, as I hear from
the same entomologist, the sexes often differ in colour. The males are
generally the brighter, and in Bombus as well as in Apathus, much more
variable in colour than the females. In Anthophora retusa the male is of a
rich fulvous-brown, whilst the female is quite black: so are the females
of several species of Xylocopa, the males being bright yellow. On the
other hand the females of some species, as of Andraena fulva, are much
brighter coloured than the males. Such differences in colour can hardly be
accounted for by the males being defenceless and thus requiring protection,
whilst the females are well defended by their stings. H. Muller (60.
'Anwendung der Darwinschen Lehre auf Bienen,' Verh. d. n. V. Jahrg. xxix.),
who has particularly attended to the habits of bees, attributes these
differences in colour in chief part to sexual selection. That bees have a
keen perception of colour is certain. He says that the males search
eagerly and fight for the possession of the females; and he accounts
through such contests for the mandibles of the males being in certain
species larger than those of the females. In some cases the males are far
more numerous than the females, either early in the season, or at all times
and places, or locally; whereas the females in other cases are apparently
in excess. In some species the more beautiful males appear to have been
selected by the females; and in others the more beautiful females by the
males. Consequently in certain genera (Muller, p. 42), the males of the
several species differ much in appearance, whilst the females are almost
indistinguishable; in other genera the reverse occurs. H. Muller believes
(p. 82) that the colours gained by one sex through sexual selection have
often been transferred in a variable degree to the other sex, just as the
pollen-collecting apparatus of the female has often been transferred to the
male, to whom it is absolutely useless. (61. M. Perrier in his article
'la Selection sexuelle d'apres Darwin' ('Revue Scientifique,' Feb. 1873, p.
868), without apparently having reflected much on the subject, objects that
as the males of social bees are known to be produced from unfertilised ova,
they could not transmit new characters to their male offspring. This is an
extraordinary objection. A female bee fertilised by a male, which
presented some character facilitating the union of the sexes, or rendering
him more attractive to the female, would lay eggs which would produce only
females; but these young females would next year produce males; and will it
be pretended that such males would not inherit the characters of their male
grandfathers? To take a case with ordinary animals as nearly parallel as
possible: if a female of any white quadruped or bird were crossed by a
male of a black breed, and the male and female offspring were paired
together, will it be pretended that the grandchildren would not inherit a
tendency to blackness from their male grandfather? The acquirement of new
characters by the sterile worker-bees is a much more difficult case, but I
have endeavoured to shew in my 'Origin of Species,' how these sterile
beings are subjected to the power of natural selection.)
Mutilla Europaea makes a stridulating noise; and according to Goureau (62.
Quoted by Westwood, 'Modern Classification of Insects,' vol. ii. p. 214.)
both sexes have this power. He attributes the sound to the friction of the
third and preceding abdominal segments, and I find that these surfaces are
marked with very fine concentric ridges; but so is the projecting thoracic
collar into which the head articulates, and this collar, when scratched
with the point of a needle, emits the proper sound. It is rather
surprising that both sexes should have the power of stridulating, as the
male is winged and the female wingless. It is notorious that Bees express
certain emotions, as of anger, by the tone of their humming; and according
to H. Muller (p. 80), the males of some species make a peculiar singing
noise whilst pursuing the females.
ORDER, COLEOPTERA (BEETLES).
Many beetles are coloured so as to resemble the surfaces which they
habitually frequent, and they thus escape detection by their enemies.
Other species, for instance diamond-beetles, are ornamented with splendid
colours, which are often arranged in stripes, spots, crosses, and other
elegant patterns. Such colours can hardly serve directly as a protection,
except in the case of certain flower-feeding species; but they may serve as
a warning or means of recognition, on the same principle as the
phosphorescence of the glow-worm. As with beetles the colours of the two
sexes are generally alike, we have no evidence that they have been gained
through sexual selection; but this is at least possible, for they have been
developed in one sex and then transferred to the other; and this view is
even in some degree probable in those groups which possess other well-
marked secondary sexual characters. Blind beetles, which cannot of course
behold each other's beauty, never, as I hear from Mr. Waterhouse, jun.,
exhibit bright colours, though they often have polished coats; but the
explanation of their obscurity may be that they generally inhabit caves and
other obscure stations.
Some Longicorns, especially certain Prionidae, offer an exception to the
rule that the sexes of beetles do not differ in colour. Most of these
insects are large and splendidly coloured. The males in the genus Pyrodes
(63. Pyrodes pulcherrimus, in which the sexes differ conspicuously, has
been described by Mr. Bates in 'Transact. Ent. Soc.' 1869, p. 50. I will
specify the few other cases in which I have heard of a difference in colour
between the sexes of beetles. Kirby and Spence ('Introduct. to
Entomology,' vol. iii. p. 301) mention a Cantharis, Meloe, Rhagium, and the
Leptura testacea; the male of the latter being testaceous, with a black
thorax, and the female of a dull red all over. These two latter beetles
belong to the family of Longicorns. Messrs. R. Trimen and Waterhouse,
jun., inform me of two Lamellicorns, viz., a Peritrichia and Trichius, the
male of the latter being more obscurely coloured than the female. In
Tillus elongatus the male is black, and the female always, as it is
believed, of a dark blue colour, with a red thorax. The male, also, of
Orsodacna atra, as I hear from Mr. Walsh, is black, the female (the so-
called O. ruficollis) having a rufous thorax.), which I saw in Mr. Bates's
collection, are generally redder but rather duller than the females, the
latter being coloured of a more or less splendid golden-green. On the
other hand, in one species the male is golden-green, the female being
richly tinted with red and purple. In the genus Esmeralda the sexes differ
so greatly in colour that they have been ranked as distinct species; in one
species both are of a beautiful shining green, but the male has a red
thorax. On the whole, as far as I could judge, the females of those
Prionidae, in which the sexes differ, are coloured more richly than the
males, and this does not accord with the common rule in regard to colour,
when acquired through sexual selection.
[Fig.16. Chalcosoma atlas.
Upper figure, male (reduced);
lower figure, female (nat. size).
Fig. 17. Copris isidis.
Fig. 18. Phanaeus faunus.
Fig. 19. Dipelicus cantori.
Fig. 20. Onthophagus rangifer, enlarged.
(In Figs. 17 to 20 the left-hand figures are males.)]
A most remarkable distinction between the sexes of many beetles is
presented by the great horns which rise from the head, thorax, and clypeus
of the males; and in some few cases from the under surface of the body.
These horns, in the great family of the Lamellicorns, resemble those of
various quadrupeds, such as stags, rhinoceroses, etc., and are wonderful
both from their size and diversified shapes. Instead of describing them, I
have given figures of the males and females of some of the more remarkable
forms. (Figs. 16 to 20.) The females generally exhibit rudiments of the
horns in the form of small knobs or ridges; but some are destitute of even
the slightest rudiment. On the other hand, the horns are nearly as well
developed in the female as in the male Phanaeus lancifer; and only a little
less well developed in the females of some other species of this genus and
of Copris. I am informed by Mr. Bates that the horns do not differ in any
manner corresponding with the more important characteristic differences
between the several subdivisions of the family: thus within the same
section of the genus Onthophagus, there are species which have a single
horn, and others which have two.
In almost all cases, the horns are remarkable from their excessive
variability; so that a graduated series can be formed, from the most highly
developed males to others so degenerate that they can barely be
distinguished from the females. Mr. Walsh (64. 'Proceedings of the
Entomological Society of Philadephia,' 1864, p. 228.) found that in
Phanaeus carnifex the horns were thrice as long in some males as in others.
Mr. Bates, after examining above a hundred males of Onthophagus rangifer
(Fig. 20), thought that he had at last discovered a species in which the
horns did not vary; but further research proved the contrary.
The extraordinary size of the horns, and their widely different structure
in closely-allied forms, indicate that they have been formed for some
purpose; but their excessive variability in the males of the same species
leads to the inference that this purpose cannot be of a definite nature.
The horns do not shew marks of friction, as if used for any ordinary work.
Some authors suppose (65. Kirby and Spence, 'Introduction to Entomology,'
vol. iii. P. 300.) that as the males wander about much more than the
females, they require horns as a defence against their enemies; but as the
horns are often blunt, they do not seem well adapted for defence. The most
obvious conjecture is that they are used by the males for fighting
together; but the males have never been observed to fight; nor could Mr.
Bates, after a careful examination of numerous species, find any sufficient
evidence, in their mutilated or broken condition, of their having been thus
used. If the males had been habitual fighters, the size of their bodies
would probably have been increased through sexual selection, so as to have
exceeded that of the females; but Mr. Bates, after comparing the two sexes
in above a hundred species of the Copridae, did not find any marked
difference in this respect amongst well-developed individuals. In Lethrus,
moreover, a beetle belonging to the same great division of the
Lamellicorns, the males are known to fight, but are not provided with
horns, though their mandibles are much larger than those of the female.
The conclusion that the horns have been acquired as ornaments is that which
best agrees with the fact of their having been so immensely, yet not
fixedly, developed,--as shewn by their extreme variability in the same
species, and by their extreme diversity in closely-allied species. This
view will at first appear extremely improbable; but we shall hereafter find
with many animals standing much higher in the scale, namely fishes,
amphibians, reptiles and birds, that various kinds of crests, knobs, horns
and combs have been developed apparently for this sole purpose.
[Fig.21. Onitis furcifer, male viewed from beneath.
Fig.22. Onitis furcifer.
Left-hand figure, male, viewed laterally.
Right-hand figure, female.
a. Rudiment of cephalic horn.
b. Trace of thoracic horn or crest.]
The males of Onitis furcifer (Fig. 21), and of some other species of the
genus, are furnished with singular projections on their anterior femora,
and with a great fork or pair of horns on the lower surface of the thorax.
Judging from other insects, these may aid the male in clinging to the
female. Although the males have not even a trace of a horn on the upper
surface of the body, yet the females plainly exhibit a rudiment of a single
horn on the head (Fig. 22, a), and of a crest (b) on the thorax. That the
slight thoracic crest in the female is a rudiment of a projection proper to
the male, though entirely absent in the male of this particular species, is
clear: for the female of Bubas bison (a genus which comes next to Onitis)
has a similar slight crest on the thorax, and the male bears a great
projection in the same situation. So, again, there can hardly be a doubt
that the little point (a) on the head of the female Onitis furcifer, as
well as on the head of the females of two or three allied species, is a
rudimentary representative of the cephalic horn, which is common to the
males of so many Lamellicorn beetles, as in Phanaeus (Fig. 18).
The old belief that rudiments have been created to complete the scheme of
nature is here so far from holding good, that we have a complete inversion
of the ordinary state of things in the family. We may reasonably suspect
that the males originally bore horns and transferred them to the females in
a rudimentary condition, as in so many other Lamellicorns. Why the males
subsequently lost their horns, we know not; but this may have been caused
through the principle of compensation, owing to the development of the
large horns and projections on the lower surface; and as these are confined
to the males, the rudiments of the upper horns on the females would not
have been thus obliterated.
[Fig. 23. Bledius taurus, magnified.
Left-hand figure, male;
right-hand figure, female.]
The cases hitherto given refer to the Lamellicorns, but the males of some
few other beetles, belonging to two widely distinct groups, namely, the
Curculionidae and Staphylinidae, are furnished with horns--in the former on
the lower surface of the body (66. Kirby and Spence, 'Introduction to
Entomology,' vol. iii. p. 329.), in the latter on the upper surface of the
head and thorax. In the Staphylinidae, the horns of the males are
extraordinarily variable in the same species, just as we have seen with the
Lamellicorns. In Siagonium we have a case of dimorphism, for the males can
be divided into two sets, differing greatly in the size of their bodies and
in the development of their horns, without intermediate gradations. In a
species of Bledius (Fig. 23), also belonging to the Staphylinidae,
Professor Westwood states that, "male specimens can be found in the same
locality in which the central horn of the thorax is very large, but the
horns of the head quite rudimental; and others, in which the thoracic horn
is much shorter, whilst the protuberances on the head are long." (67.
'Modern Classification of Insects,' vol. i. p. 172: Siagonium, p. 172. In
the British Museum I noticed one male specimen of Siagonium in an
intermediate condition, so that the dimorphism is not strict.) Here we
apparently have a case of compensation, which throws light on that just
given, of the supposed loss of the upper horns by the males of Onitis.
LAW OF BATTLE.
Some male beetles, which seem ill-fitted for fighting, nevertheless engage
in conflicts for the possession of the females. Mr. Wallace (68. 'The
Malay Archipelago,' vol. ii. 1869, p. 276. Riley, Sixth 'Report on Insects
of Missouri,' 1874, p. 115.) saw two males of Leptorhynchus angustatus, a
linear beetle with a much elongated rostrum, "fighting for a female, who
stood close by busy at her boring. They pushed at each other with their
rostra, and clawed and thumped, apparently in the greatest rage." The
smaller male, however, "soon ran away, acknowledging himself vanquished."
In some few cases male beetles are well adapted for fighting, by possessing
great toothed mandibles, much larger than those of the females. This is
the case with the common stag-beetle (Lucanus cervus), the males of which
emerge from the pupal state about a week before the other sex, so that
several may often be seen pursuing the same female. At this season they
engage in fierce conflicts. When Mr. A.H. Davis (69. 'Entomological
Magazine,' vol. i. 1833, p. 82. See also on the conflicts of this species,
Kirby and Spence, ibid. vol. iii. p. 314; and Westwood, ibid. vol. i. p.
187.) enclosed two males with one female in a box, the larger male severely
pinched the smaller one, until he resigned his pretensions. A friend
informs me that when a boy he often put the males together to see them
fight, and he noticed that they were much bolder and fiercer than the
females, as with the higher animals. The males would seize hold of his
finger, if held in front of them, but not so the females, although they
have stronger jaws. The males of many of the Lucanidae, as well as of the
above-mentioned Leptorhynchus, are larger and more powerful insects than
the females. The two sexes of Lethrus cephalotes (one of the Lamellicorns)
inhabit the same burrow; and the male has larger mandibles than the female.
If, during the breeding-season, a strange male attempts to enter the
burrow, he is attacked; the female does not remain passive, but closes the
mouth of the burrow, and encourages her mate by continually pushing him on
from behind; and the battle lasts until the aggressor is killed or runs
away. (70. Quoted from Fischer, in 'Dict. Class. d'Hist. Nat.' tom. x. p.
324.) The two sexes of another Lamellicorn beetle, the Ateuchus
cicatricosus, live in pairs, and seem much attached to each other; the male
excites the females to roll the balls of dung in which the ova are
deposited; and if she is removed, he becomes much agitated. If the male is
removed the female ceases all work, and as M. Brulerie believes, would
remain on the same spot until she died. (71. 'Ann. Soc. Entomolog.
France,' 1866, as quoted in 'Journal of Travel,' by A. Murray, 1868, p.
135.)
[Fig. 24. Chiasognathus Grantii, reduced.
Upper figure, male;
lower figure, female.]
The great mandibles of the male Lucanidae are extremely variable both in
size and structure, and in this respect resemble the horns on the head and
thorax of many male Lamellicorns and Staphylinidae. A perfect series can
be formed from the best-provided to the worst-provided or degenerate males.
Although the mandibles of the common stag-beetle, and probably of many
other species, are used as efficient weapons for fighting, it is doubtful
whether their great size can thus be accounted for. We have seen that they
are used by the Lucanus elaphus of N. America for seizing the female. As
they are so conspicuous and so elegantly branched, and as owing to their
great length they are not well adapted for pinching, the suspicion has
crossed my mind that they may in addition serve as an ornament, like the
horns on the head and thorax of the various species above described. The
male Chiasognathus grantii of S. Chile--a splendid beetle belonging to the
same family--has enormously developed mandibles (Fig. 24); he is bold and
pugnacious; when threatened he faces round, opens his great jaws, and at
the same time stridulates loudly. But the mandibles were not strong enough
to pinch my finger so as to cause actual pain.
Sexual selection, which implies the possession of considerable perceptive
powers and of strong passions, seems to have been more effective with the
Lamellicorns than with any other family of beetles. With some species the
males are provided with weapons for fighting; some live in pairs and shew
mutual affection; many have the power of stridulating when excited; many
are furnished with the most extraordinary horns, apparently for the sake of
ornament; and some, which are diurnal in their habits, are gorgeously
coloured. Lastly, several of the largest beetles in the world belong to
this family, which was placed by Linnaeus and Fabricius as the head of the
Order. (72. Westwood, 'Modern Classification,' vol. i. p. 184.)
STRIDULATING ORGANS.
Beetles belonging to many and widely distinct families possess these
organs. The sound thus produced can sometimes be heard at the distance of
several feet or even yards (73. Wollaston, 'On Certain Musical
Curculionidae,' 'Annals and Mag. of Nat. Hist.' vol. vi. 1860, p. 14.), but
it is not comparable with that made by the Orthoptera. The rasp generally
consists of a narrow, slightly-raised surface, crossed by very fine,
parallel ribs, sometimes so fine as to cause iridescent colours, and having
a very elegant appearance under the microscope. In some cases, as with
Typhoeus, minute, bristly or scale-like prominences, with which the whole
surrounding surface is covered in approximately parallel lines, could be
traced passing into the ribs of the rasp. The transition takes place by
their becoming confluent and straight, and at the same time more prominent
and smooth. A hard ridge on an adjoining part of the body serves as the
scraper for the rasp, but this scraper in some cases has been specially
modified for the purpose. It is rapidly moved across the rasp, or
conversely the rasp across the scraper.
[Fig.25. Necrophorus (from Landois).
r. The two rasps.
Left-hand figure, part of the rasp highly magnified.]
These organs are situated in widely different positions. In the carrion-
beetles (Necrophorus) two parallel rasps (r, Fig. 25) stand on the dorsal
surface of the fifth abdominal segment, each rasp (74. Landois,
'Zeitschrift fur wissenschaft Zoolog.' B. xvii. 1867, s. 127.) consisting
of 126 to 140 fine ribs. These ribs are scraped against the posterior
margins of the elytra, a small portion of which projects beyond the general
outline. In many Crioceridae, and in Clythra 4-punctata (one of the
Chrysomelidae), and in some Tenebrionidae, etc. (75. I am greatly indebted
to Mr. G.R. Crotch for having sent me many prepared specimens of various
beetles belonging to these three families and to others, as well as for
valuable information. He believes that the power of stridulation in the
Clythra has not been previously observed. I am also much indebted to Mr.
E.W. Janson, for information and specimens. I may add that my son, Mr. F.
Darwin, finds that Dermestes murinus stridulates, but he searched in vain
for the apparatus. Scolytus has lately been described by Dr. Chapman as a
stridulator, in the 'Entomologist's Monthly Magazine,' vol. vi. p. 130.),
the rasp is seated on the dorsal apex of the abdomen, on the pygidium or
pro-pygidium, and is scraped in the same manner by the elytra. In
Heterocerus, which belongs to another family, the rasps are placed on the
sides of the first abdominal segment, and are scraped by ridges on the
femora. (76. Schiodte, translated, in 'Annals and Magazine of Natural
History,' vol. xx. 1867, p. 37.) In certain Curculionidae and Carabidae
(77. Westring has described (Kroyer, 'Naturhist. Tidskrift,' B. ii. 1848-
49, p. 334) the stridulating organs in these two, as well as in other
families. In the Carabidae I have examined Elaphrus uliginosus and
Blethisa multipunctata, sent to me by Mr. Crotch. In Blethisa the
transverse ridges on the furrowed border of the abdominal segment do not,
as far as I could judge, come into play in scraping the rasps on the
elytra.), the parts are completely reversed in position, for the rasps are
seated on the inferior surface of the elytra, near their apices, or along
their outer margins, and the edges of the abdominal segments serve as the
scrapers. In Pelobius Hermanni (one of Dytiscidae or water-beetles) a
strong ridge runs parallel and near to the sutural margin of the elytra,
and is crossed by ribs, coarse in the middle part, but becoming gradually
finer at both ends, especially at the upper end; when this insect is held
under water or in the air, a stridulating noise is produced by the extreme
horny margin of the abdomen being scraped against the rasps. In a great
number of long-horned beetles (Longicornia) the organs are situated quite
otherwise, the rasp being on the meso-thorax, which is rubbed against the
pro-thorax; Landois counted 238 very fine ribs on the rasp of Cerambyx
heros.
[Fig.26. Hind-leg of Geotrupes stercorarius (from Landois).
r. Rasp. c. Coxa. f. Femur. t. Tibia. tr. Tarsi.]
Many Lamellicorns have the power of stridulating, and the organs differ
greatly in position. Some species stridulate very loudly, so that when Mr.
F. Smith caught a Trox sabulosus, a gamekeeper, who stood by, thought he
had caught a mouse; but I failed to discover the proper organs in this
beetle. In Geotrupes and Typhoeus, a narrow ridge runs obliquely across
(r, Fig. 26) the coxa of each hind-leg (having in G. stercorarius 84 ribs),
which is scraped by a specially projecting part of one of the abdominal
segments. In the nearly allied Copris lunaris, an excessively narrow fine
rasp runs along the sutural margin of the elytra, with another short rasp
near the basal outer margin; but in some other Coprini the rasp is seated,
according to Leconte (78. I am indebted to Mr. Walsh, of Illinois, for
having sent me extracts from Leconte's 'Introduction to Entomology,' pp.
101, 143.), on the dorsal surface of the abdomen. In Oryctes it is seated
on the pro-pygidium; and, according to the same entomologist, in some other
Dynastini, on the under surface of the elytra. Lastly, Westring states
that in Omaloplia brunnea the rasp is placed on the pro-sternum, and the
scraper on the meta-sternum, the parts thus occupying the under surface of
the body, instead of the upper surface as in the Longicorns.
We thus see that in the different coleopterous families the stridulating
organs are wonderfully diversified in position, but not much in structure.
Within the same family some species are provided with these organs, and
others are destitute of them. This diversity is intelligible, if we
suppose that originally various beetles made a shuffling or hissing noise
by the rubbing together of any hard and rough parts of their bodies, which
happened to be in contact; and that from the noise thus produced being in
some way useful, the rough surfaces were gradually developed into regular
stridulating organs. Some beetles as they move, now produce, either
intentionally or unintentionally, a shuffling noise, without possessing any
proper organs for the purpose. Mr. Wallace informs me that the Euchirus
longimanus (a Lamellicorn, with the anterior legs wonderfully elongated in
the male) "makes, whilst moving, a low hissing sound by the protrusion and
contraction of the abdomen; and when seized it produces a grating sound by
rubbing its hind-legs against the edges of the elytra." The hissing sound
is clearly due to a narrow rasp running along the sutural margin of each
elytron; and I could likewise make the grating sound by rubbing the
shagreened surface of the femur against the granulated margin of the
corresponding elytron; but I could not here detect any proper rasp; nor is
it likely that I could have overlooked it in so large an insect. After
examining Cychrus, and reading what Westring has written about this beetle,
it seems very doubtful whether it possesses any true rasp, though it has
the power of emitting a sound.
From the analogy of the Orthoptera and Homoptera, I expected to find the
stridulating organs in the Coleoptera differing according to sex; but
Landois, who has carefully examined several species, observed no such
difference; nor did Westring; nor did Mr. G.R. Crotch in preparing the many
specimens which he had the kindness to send me. Any difference in these
organs, if slight, would, however, be difficult to detect, on account of
their great variability. Thus, in the first pair of specimens of
Necrophorus humator and of Pelobius which I examined, the rasp was
considerably larger in the male than in the female; but not so with
succeeding specimens. In Geotrupes stercorarius the rasp appeared to me
thicker, opaquer, and more prominent in three males than in the same number
of females; in order, therefore, to discover whether the sexes differed in
their power of stridulating, my son, Mr. F. Darwin, collected fifty-seven
living specimens, which he separated into two lots, according as they made
a greater or lesser noise, when held in the same manner. He then examined
all these specimens, and found that the males were very nearly in the same
proportion to the females in both the lots. Mr. F. Smith has kept alive
numerous specimens of Monoynchus pseudacori (Curculionidae), and is
convinced that both sexes stridulate, and apparently in an equal degree.
Nevertheless, the power of stridulating is certainly a sexual character in
some few Coleoptera. Mr. Crotch discovered that the males alone of two
species of Heliopathes (Tenebrionidae) possess stridulating organs. I
examined five males of H. gibbus, and in all these there was a well-
developed rasp, partially divided into two, on the dorsal surface of the
terminal abdominal segment; whilst in the same number of females there was
not even a rudiment of the rasp, the membrane of this segment being
transparent, and much thinner than in the male. In H. cribratostriatus the
male has a similar rasp, excepting that it is not partially divided into
two portions, and the female is completely destitute of this organ; the
male in addition has on the apical margins of the elytra, on each side of
the suture, three or four short longitudinal ridges, which are crossed by
extremely fine ribs, parallel to and resembling those on the abdominal
rasp; whether these ridges serve as an independent rasp, or as a scraper
for the abdominal rasp, I could not decide: the female exhibits no trace
of this latter structure.
Again, in three species of the Lamellicorn genus Oryctes, we have a nearly
parallel case. In the females of O. gryphus and nasicornis the ribs on the
rasp of the pro-pygidium are less continuous and less distinct than in the
males; but the chief difference is that the whole upper surface of this
segment, when held in the proper light, is seen to be clothed with hairs,
which are absent or are represented by excessively fine down in the males.
It should be noticed that in all Coleoptera the effective part of the rasp
is destitute of hairs. In O. senegalensis the difference between the sexes
is more strongly marked, and this is best seen when the proper abdominal
segment is cleaned and viewed as a transparent object. In the female the
whole surface is covered with little separate crests, bearing spines;
whilst in the male these crests in proceeding towards the apex, become more
and more confluent, regular, and naked; so that three-fourths of the
segment is covered with extremely fine parallel ribs, which are quite
absent in the female. In the females, however, of all three species of
Oryctes, a slight grating or stridulating sound is produced, when the
abdomen of a softened specimen is pushed backwards and forwards.
In the case of the Heliopathes and Oryctes there can hardly be a doubt that
the males stridulate in order to call or to excite the females; but with
most beetles the stridulation apparently serves both sexes as a mutual
call. Beetles stridulate under various emotions, in the same manner as
birds use their voices for many purposes besides singing to their mates.
The great Chiasognathus stridulates in anger or defiance; many species do
the same from distress or fear, if held so that they cannot escape; by
striking the hollow stems of trees in the Canary Islands, Messrs. Wollaston
and Crotch were able to discover the presence of beetles belonging to the
genus Acalles by their stridulation. Lastly, the male Ateuchus stridulates
to encourage the female in her work, and from distress when she is removed.
(79. M. P. de la Brulerie, as quoted in 'Journal of Travel,' A. Murray,
vol. i. 1868, p. 135.) Some naturalists believe that beetles make this
noise to frighten away their enemies; but I cannot think that a quadruped
or bird, able to devour a large beetle, would be frightened by so slight a
sound. The belief that the stridulation serves as a sexual call is
supported by the fact that death-ticks (Anobium tessellatum) are well known
to answer each other's ticking, and, as I have myself observed, a tapping
noise artificially made. Mr. Doubleday also informs me that he has
sometimes observed a female ticking (80. According to Mr. Doubleday, "the
noise is produced by the insect raising itself on its legs as high as it
can, and then striking its thorax five or six times, in rapid succession,
against the substance upon which it is sitting." For references on this
subject see Landois, 'Zeitschrift fur wissen. Zoolog.' B. xvii. s. 131.
Olivier says (as quoted by Kirby and Spence, 'Introduction to Entomology,'
vol. ii. p. 395) that the female of Pimelia striata produces a rather loud
sound by striking her abdomen against any hard substance, "and that the
male, obedient to this call, soon attends her, and they pair."), and in an
hour or two afterwards has found her united with a male, and on one
occasion surrounded by several males. Finally, it is probable that the two
sexes of many kinds of beetles were at first enabled to find each other by
the slight shuffling noise produced by the rubbing together of the
adjoining hard parts of their bodies; and that as those males or females
which made the greatest noise succeeded best in finding partners,
rugosities on various parts of their bodies were gradually developed by
means of sexual selection into true stridulating organs.
CHAPTER XI.
INSECTS, continued.
ORDER LEPIDOPTERA. (BUTTERFLIES AND MOTHS.)
Courtship of butterflies--Battles--Ticking noise--Colours common to both
sexes, or more brilliant in the males--Examples--Not due to the direct
action of the conditions of life--Colours adapted for protection--Colours
of moths--Display--Perceptive powers of the Lepidoptera--Variability--
Causes of the difference in colour between the males and females--Mimicry,
female butterflies more brilliantly coloured than the males--Bright colours
of caterpillars--Summary and concluding remarks on the secondary sexual
characters of insects--Birds and insects compared.
In this great Order the most interesting points for us are the differences
in colour between the sexes of the same species, and between the distinct
species of the same genus. Nearly the whole of the following chapter will
be devoted to this subject; but I will first make a few remarks on one or
two other points. Several males may often be seen pursuing and crowding
round the same female. Their courtship appears to be a prolonged affair,
for I have frequently watched one or more males pirouetting round a female
until I was tired, without seeing the end of the courtship. Mr. A.G.
Butler also informs me that he has several times watched a male courting a
female for a full quarter of an hour; but she pertinaciously refused him,
and at last settled on the ground and closed her wings, so as to escape
from his addresses.
Although butterflies are weak and fragile creatures, they are pugnacious,
and an emperor butterfly (1. Apatura Iris: 'The Entomologist's Weekly
Intelligence,' 1859, p. 139. For the Bornean Butterflies, see C.
Collingwood, 'Rambles of a Naturalist,' 1868, p. 183.) has been captured
with the tips of its wings broken from a conflict with another male. Mr.
Collingwood, in speaking of the frequent battles between the butterflies of
Borneo, says, "They whirl round each other with the greatest rapidity, and
appear to be incited by the greatest ferocity."
The Ageronia feronia makes a noise like that produced by a toothed wheel
passing under a spring catch, and which can be heard at the distance of
several yards: I noticed this sound at Rio de Janeiro, only when two of
these butterflies were chasing each other in an irregular course, so that
it is probably made during the courtship of the sexes. (2. See my
'Journal of Researches,' 1845, p. 33. Mr. Doubleday has detected ('Proc.
Ent. Soc.' March 3, 1845, p. 123) a peculiar membranous sac at the base of
the front wings, which is probably connected with the production of the
sound. For the case of Thecophora, see 'Zoological Record,' 1869, p. 401.
For Mr. Buchanan White's observations, the Scottish Naturalist, July 1872,
p. 214.)
Some moths also produce sounds; for instance, the males Theocophora fovea.
On two occasions Mr. F. Buchanan White (3. 'The Scottish Naturalist,' July
1872, p. 213.) heard a sharp quick noise made by the male of Hylophila
prasinana, and which he believes to be produced, as in Cicada, by an
elastic membrane, furnished with a muscle. He quotes, also, Guenee, that
Setina produces a sound like the ticking of a watch, apparently by the aid
of "two large tympaniform vesicles, situated in the pectoral region"; and
these "are much more developed in the male than in the female." Hence the
sound-producing organs in the Lepidoptera appear to stand in some relation
with the sexual functions. I have not alluded to the well-known noise made
by the Death's Head Sphinx, for it is generally heard soon after the moth
has emerged from its cocoon.
Giard has always observed that the musky odour, which is emitted by two
species of Sphinx moths, is peculiar to the males (4. 'Zoological Record,'
1869, p. 347.); and in the higher classes we shall meet with many instances
of the males alone being odoriferous.
Every one must have admired the extreme beauty of many butterflies and of
some moths; and it may be asked, are their colours and diversified patterns
the result of the direct action of the physical conditions to which these
insects have been exposed, without any benefit being thus derived? Or have
successive variations been accumulated and determined as a protection, or
for some unknown purpose, or that one sex may be attractive to the other?
And, again, what is the meaning of the colours being widely different in
the males and females of certain species, and alike in the two sexes of
other species of the same genus? Before attempting to answer these
questions a body of facts must be given.
With our beautiful English butterflies, the admiral, peacock, and painted
lady (Vanessae), as well as many others, the sexes are alike. This is also
the case with the magnificent Heliconidae, and most of the Danaidae in the
tropics. But in certain other tropical groups, and in some of our English
butterflies, as the purple emperor, orange-tip, etc. (Apatura Iris and
Anthocharis cardamines), the sexes differ either greatly or slightly in
colour. No language suffices to describe the splendour of the males of
some tropical species. Even within the same genus we often find species
presenting extraordinary differences between the sexes, whilst others have
their sexes closely alike. Thus in the South American genus Epicalia, Mr.
Bates, to whom I am indebted for most of the following facts, and for
looking over this whole discussion, informs me that he knows twelve
species, the two sexes of which haunt the same stations (and this is not
always the case with butterflies), and which, therefore, cannot have been
differently affected by external conditions. (5. See also Mr. Bates's
paper in 'Proc. Ent. Soc. of Philadelphia,' 1865, p. 206. Also Mr. Wallace
on the same subject, in regard to Diadema, in 'Transactions, Entomological
Society of London,' 1869, p. 278.) In nine of these twelve species the
males rank amongst the most brilliant of all butterflies, and differ so
greatly from the comparatively plain females that they were formerly placed
in distinct genera. The females of these nine species resemble each other
in their general type of coloration; and they likewise resemble both sexes
of the species in several allied genera found in various parts of the
world. Hence we may infer that these nine species, and probably all the
others of the genus, are descended from an ancestral form which was
coloured in nearly the same manner. In the tenth species the female still
retains the same general colouring, but the male resembles her, so that he
is coloured in a much less gaudy and contrasted manner than the males of
the previous species. In the eleventh and twelfth species, the females
depart from the usual type, for they are gaily decorated almost like the
males, but in a somewhat less degree. Hence in these two latter species
the bright colours of the males seem to have been transferred to the
females; whilst in the tenth species the male has either retained or
recovered the plain colours of the female, as well as of the parent-form of
the genus. The sexes in these three cases have thus been rendered nearly
alike, though in an opposite manner. In the allied genus Eubagis, both
sexes of some of the species are plain-coloured and nearly alike; whilst
with the greater number the males are decorated with beautiful metallic
tints in a diversified manner, and differ much from their females. The
females throughout the genus retain the same general style of colouring, so
that they resemble one another much more closely than they resemble their
own males.
In the genus Papilio, all the species of the Aeneas group are remarkable
for their conspicuous and strongly contrasted colours, and they illustrate
the frequent tendency to gradation in the amount of difference between the
sexes. In a few species, for instance in P. ascanius, the males and
females are alike; in others the males are either a little brighter, or
very much more superb than the females. The genus Junonia, allied to our
Vanessae, offers a nearly parallel case, for although the sexes of most of
the species resemble each other, and are destitute of rich colours, yet in
certain species, as in J. oenone, the male is rather more bright-coloured
than the female, and in a few (for instance J. andremiaja) the male is so
different from the female that he might be mistaken for an entirely
distinct species.
Another striking case was pointed out to me in the British Museum by Mr. A.
Butler, namely, one of the tropical American Theclae, in which both sexes
are nearly alike and wonderfully splendid; in another species the male is
coloured in a similarly gorgeous manner, whilst the whole upper surface of
the female is of a dull uniform brown. Our common little English blue
butterflies of the genus Lycaena, illustrate the various differences in
colour between the sexes, almost as well, though not in so striking a
manner, as the above exotic genera. In Lycaena agestis both sexes have
wings of a brown colour, bordered with small ocellated orange spots, and
are thus alike. In L. oegon the wings of the males are of a fine blue,
bordered with black, whilst those of the female are brown, with a similar
border, closely resembling the wings of L. agestis. Lastly, in L. arion
both sexes are of a blue colour and are very like, though in the female the
edges of the wings are rather duskier, with the black spots plainer; and in
a bright blue Indian species both sexes are still more alike.
I have given the foregoing details in order to shew, in the first place,
that when the sexes of butterflies differ, the male as a general rule is
the more beautiful, and departs more from the usual type of colouring of
the group to which the species belongs. Hence in most groups the females
of the several species resemble each other much more closely than do the
males. In some cases, however, to which I shall hereafter allude, the
females are coloured more splendidly than the males. In the second place,
these details have been given to bring clearly before the mind that within
the same genus, the two sexes frequently present every gradation from no
difference in colour, to so great a difference that it was long before the
two were placed by entomologists in the same genus. In the third place, we
have seen that when the sexes nearly resemble each other, this appears due
either to the male having transferred his colours to the female, or to the
male having retained, or perhaps recovered, the primordial colours of the
group. It also deserves notice that in those groups in which the sexes
differ, the females usually somewhat resemble the males, so that when the
males are beautiful to an extraordinary degree, the females almost
invariably exhibit some degree of beauty. From the many cases of gradation
in the amount of difference between the sexes, and from the prevalence of
the same general type of coloration throughout the whole of the same group,
we may conclude that the causes have generally been the same which have
determined the brilliant colouring of the males alone of some species, and
of both sexes of other species.
As so many gorgeous butterflies inhabit the tropics, it has often been
supposed that they owe their colours to the great heat and moisture of
these zones; but Mr. Bates (6. 'The Naturalist on the Amazons,' vol. i.
1863, p. 19.) has shown by the comparison of various closely-allied groups
of insects from the temperate and tropical regions, that this view cannot
be maintained; and the evidence becomes conclusive when brilliantly-
coloured males and plain-coloured females of the same species inhabit the
same district, feed on the same food, and follow exactly the same habits of
life. Even when the sexes resemble each other, we can hardly believe that
their brilliant and beautifully-arranged colours are the purposeless result
of the nature of the tissues and of the action of the surrounding
conditions.
With animals of all kinds, whenever colour has been modified for some
special purpose, this has been, as far as we can judge, either for direct
or indirect protection, or as an attraction between the sexes. With many
species of butterflies the upper surfaces of the wings are obscure; and
this in all probability leads to their escaping observation and danger.
But butterflies would be particularly liable to be attacked by their
enemies when at rest; and most kinds whilst resting raise their wings
vertically over their backs, so that the lower surface alone is exposed to
view. Hence it is this side which is often coloured so as to imitate the
objects on which these insects commonly rest. Dr. Rossler, I believe,
first noticed the similarity of the closed wings of certain Vanessae and
other butterflies to the bark of trees. Many analogous and striking facts
could be given. The most interesting one is that recorded by Mr. Wallace
(7. See the interesting article in the 'Westminster Review,' July 1867, p.
10. A woodcut of the Kallima is given by Mr. Wallace in 'Hardwicke's
Science Gossip,' September 1867, p. 196.) of a common Indian and Sumatran
butterfly (Kallima) which disappears like magic when it settles on a bush;
for it hides its head and antennae between its closed wings, which, in
form, colour and veining, cannot be distinguished from a withered leaf with
its footstalk. In some other cases the lower surfaces of the wings are
brilliantly coloured, and yet are protective; thus in Thecla rubi the wings
when closed are of an emerald green, and resemble the young leaves of the
bramble, on which in spring this butterfly may often be seen seated. It is
also remarkable that in very many species in which the sexes differ greatly
in colour on their upper surface, the lower surface is closely similar or
identical in both sexes, and serves as a protection. (8. Mr. G. Fraser,
in 'Nature,' April 1871, p. 489.)
Although the obscure tints both of the upper and under sides of many
butterflies no doubt serve to conceal them, yet we cannot extend this view
to the brilliant and conspicuous colours on the upper surface of such
species as our admiral and peacock Vanessae, our white cabbage-butterflies
(Pieris), or the great swallow-tail Papilio which haunts the open fens--for
these butterflies are thus rendered visible to every living creature. In
these species both sexes are alike; but in the common brimstone butterfly
(Gonepteryx rhamni), the male is of an intense yellow, whilst the female is
much paler; and in the orange-tip (Anthocharis cardamines) the males alone
have their wings tipped with bright orange. Both the males and females in
these cases are conspicuous, and it is not credible that their difference
in colour should stand in any relation to ordinary protection. Prof.
Weismann remarks (9. 'Einfluss der Isolirung auf die Artbildung,' 1872, p.
58.), that the female of one of the Lycaenae expands her brown wings when
she settles on the ground, and is then almost invisible; the male, on the
other hand, as if aware of the danger incurred from the bright blue of the
upper surface of his wings, rests with them closed; and this shows that the
blue colour cannot be in any way protective. Nevertheless, it is probable
that conspicuous colours are indirectly beneficial to many species, as a
warning that they are unpalatable. For in certain other cases, beauty has
been gained through the imitation of other beautiful species, which inhabit
the same district and enjoy an immunity from attack by being in some way
offensive to their enemies; but then we have to account for the beauty of
the imitated species.
As Mr. Walsh has remarked to me, the females of our orange-tip butterfly,
above referred to, and of an American species (Anth. genutia) probably shew
us the primordial colours of the parent-species of the genus; for both
sexes of four or five widely-distributed species are coloured in nearly the
same manner. As in several previous cases, we may here infer that it is
the males of Anth. cardamines and genutia which have departed from the
usual type of the genus. In the Anth. sara from California, the orange-
tips to the wings have been partially developed in the female; but they are
paler than in the male, and slightly different in some other respects. In
an allied Indian form, the Iphias glaucippe, the orange-tips are fully
developed in both sexes. In this Iphias, as pointed out to me by Mr. A.
Butler, the under surface of the wings marvellously resembles a pale-
coloured leaf; and in our English orange-tip, the under surface resembles
the flower-head of the wild parsley, on which the butterfly often rests at
night. (10. See the interesting observations by T.W. Wood, 'The Student,'
Sept. 1868, p. 81.) The same reason which compels us to believe that the
lower surfaces have here been coloured for the sake of protection, leads us
to deny that the wings have been tipped with bright orange for the same
purpose, especially when this character is confined to the males.
Most Moths rest motionless during the whole or greater part of the day with
their wings depressed; and the whole upper surface is often shaded and
coloured in an admirable manner, as Mr. Wallace has remarked, for escaping
detection. The front-wings of the Bombycidae and Noctuidae (11. Mr.
Wallace in 'Hardwicke's Science Gossip,' September 1867, p. 193.), when at
rest, generally overlap and conceal the hind-wings; so that the latter
might be brightly coloured without much risk; and they are in fact often
thus coloured. During flight, moths would often be able to escape from
their enemies; nevertheless, as the hind-wings are then fully exposed to
view, their bright colours must generally have been acquired at some little
risk. But the following fact shews how cautious we ought to be in drawing
conclusions on this head. The common Yellow Under-wings (Triphaena) often
fly about during the day or early evening, and are then conspicuous from
the colour of their hind-wings. It would naturally be thought that this
would be a source of danger; but Mr. J. Jenner Weir believes that it
actually serves them as a means of escape, for birds strike at these
brightly coloured and fragile surfaces, instead of at the body. For
instance, Mr. Weir turned into his aviary a vigorous specimen of Triphaena
pronuba, which was instantly pursued by a robin; but the bird's attention
being caught by the coloured wings, the moth was not captured until after
about fifty attempts, and small portions of the wings were repeatedly
broken off. He tried the same experiment, in the open air, with a swallow
and T. fimbria; but the large size of this moth probably interfered with
its capture. (12. See also, on this subject, Mr. Weir's paper in
'Transactions, Entomological Society,' 1869, p. 23.) We are thus reminded
of a statement made by Mr. Wallace (13. 'Westminster Review,' July 1867,
p. 16.), namely, that in the Brazilian forests and Malayan islands, many
common and highly-decorated butterflies are weak flyers, though furnished
with a broad expanse of wing; and they "are often captured with pierced and
broken wings, as if they had been seized by birds, from which they had
escaped: if the wings had been much smaller in proportion to the body, it
seems probable that the insect would more frequently have been struck or
pierced in a vital part, and thus the increased expanse of the wings may
have been indirectly beneficial."
DISPLAY.
The bright colours of many butterflies and of some moths are specially
arranged for display, so that they may be readily seen. During the night
colours are not visible, and there can be no doubt that the nocturnal
moths, taken as a body, are much less gaily decorated than butterflies, all
of which are diurnal in their habits. But the moths of certain families,
such as the Zygaenidae, several Sphingidae, Uraniidae, some Arctiidae and
Saturniidae, fly about during the day or early evening, and many of these
are extremely beautiful, being far brighter coloured than the strictly
nocturnal kinds. A few exceptional cases, however, of bright-coloured
nocturnal species have been recorded. (14. For instance, Lithosia; but
Prof. Westwood ('Modern Class. of Insects,' vol. ii. p. 390) seems
surprised at this case. On the relative colours of diurnal and nocturnal
Lepidoptera, see ibid. pp. 333 and 392; also Harris, 'Treatise on the
Insects of New England,' 1842, p. 315.)
There is evidence of another kind in regard to display. Butterflies, as
before remarked, elevate their wings when at rest, but whilst basking in
the sunshine often alternately raise and depress them, thus exposing both
surfaces to full view; and although the lower surface is often coloured in
an obscure manner as a protection, yet in many species it is as highly
decorated as the upper surface, and sometimes in a very different manner.
In some tropical species the lower surface is even more brilliantly
coloured than the upper. (15. Such differences between the upper and
lower surfaces of the wings of several species of Papilio may be seen in
the beautiful plates to Mr. Wallace's 'Memoir on the Papilionidae of the
Malayan Region,' in 'Transactions of the Linnean Society,' vol. xxv. part
i. 1865.) In the English fritillaries (Argynnis) the lower surface alone
is ornamented with shining silver. Nevertheless, as a general rule, the
upper surface, which is probably more fully exposed, is coloured more
brightly and diversely than the lower. Hence the lower surface generally
affords to entomologists the more useful character for detecting the
affinities of the various species. Fritz Muller informs me that three
species of Castnia are found near his house in S. Brazil: of two of them
the hind-wings are obscure, and are always covered by the front-wings when
these butterflies are at rest; but the third species has black hind-wings,
beautifully spotted with red and white, and these are fully expanded and
displayed whenever the butterfly rests. Other such cases could be added.
If we now turn to the enormous group of moths, which, as I hear from Mr.
Stainton, do not habitually expose the under surface of their wings to full
view, we find this side very rarely coloured with a brightness greater
than, or even equal to, that of the upper side. Some exceptions to the
rule, either real or apparent, must be noticed, as the case of Hypopyra.
(16. See Mr. Wormald on this moth: 'Proceedings of the Entomological
Society,' March 2, 1868.) Mr. Trimen informs me that in Guenee's great
work, three moths are figured, in which the under surface is much the more
brilliant. For instance, in the Australian Gastrophora the upper surface
of the fore-wing is pale greyish-ochreous, while the lower surface is
magnificently ornamented by an ocellus of cobalt-blue, placed in the midst
of a black mark, surrounded by orange-yellow, and this by bluish-white.
But the habits of these three moths are unknown; so that no explanation can
be given of their unusual style of colouring. Mr. Trimen also informs me
that the lower surface of the wings in certain other Geometrae (17. See
also an account of the S. American genus Erateina (one of the Geometrae) in
'Transactions, Ent. Soc.' new series, vol. v. pl. xv. and xvi.) and
quadrifid Noctuae are either more variegated or more brightly-coloured than
the upper surface; but some of these species have the habit of "holding
their wings quite erect over their backs, retaining them in this position
for a considerable time," and thus exposing the under surface to view.
Other species, when settled on the ground or herbage, now and then suddenly
and slightly lift up their wings. Hence the lower surface of the wings
being brighter than the upper surface in certain moths is not so anomalous
as it at first appears. The Saturniidae include some of the most beautiful
of all moths, their wings being decorated, as in our British Emperor moth,
with fine ocelli; and Mr. T.W. Wood (18. 'Proc Ent. Soc. of London,' July
6, 1868, p. xxvii.) observes that they resemble butterflies in some of
their movements; "for instance, in the gentle waving up and down of the
wings as if for display, which is more characteristic of diurnal than of
nocturnal Lepidoptera."
It is a singular fact that no British moths which are brilliantly coloured,
and, as far as I can discover, hardly any foreign species, differ much in
colour according to sex; though this is the case with many brilliant
butterflies. The male, however, of one American moth, the Saturnia Io, is
described as having its fore-wings deep yellow, curiously marked with
purplish-red spots; whilst the wings of the female are purple-brown, marked
with grey lines. (19. Harris, 'Treatise,' etc., edited by Flint, 1862, p.
395.) The British moths which differ sexually in colour are all brown, or
of various dull yellow tints, or nearly white. In several species the
males are much darker than the females (20. For instance, I observe in my
son's cabinet that the males are darker than the females in the Lasiocampa
quercus, Odonestis potatoria, Hypogymna dispar, Dasychira pudibunda, and
Cycnia mendica. In this latter species the difference in colour between
the two sexes is strongly marked; and Mr. Wallace informs me that we here
have, as he believes, an instance of protective mimicry confined to one
sex, as will hereafter be more fully explained. The white female of the
Cycnia resembles the very common Spilosoma menthrasti, both sexes of which
are white; and Mr. Stainton observed that this latter moth was rejected
with utter disgust by a whole brood of young turkeys, which were fond of
eating other moths; so that if the Cycnia was commonly mistaken by British
birds for the Spilosoma, it would escape being devoured, and its white
deceptive colour would thus be highly beneficial.), and these belong to
groups which generally fly about during the afternoon. On the other hand,
in many genera, as Mr. Stainton informs me, the males have the hind-wings
whiter than those of the female--of which fact Agrotis exclamationis offers
a good instance. In the Ghost Moth (Hepialus humuli) the difference is
more strongly marked; the males being white, and the females yellow with
darker markings. (21. It is remarkable, that in the Shetland Islands the
male of this moth, instead of differing widely from the female, frequently
resembles her closely in colour (see Mr. MacLachlan, 'Transactions,
Entomological Society,' vol. ii. 1866, p. 459). Mr. G. Fraser suggests
('Nature,' April 1871, p. 489) that at the season of the year when the
ghost-moth appears in these northern islands, the whiteness of the males
would not be needed to render them visible to the females in the twilight
night.) It is probable that in these cases the males are thus rendered
more conspicuous, and more easily seen by the females whilst flying about
in the dusk.
From the several foregoing facts it is impossible to admit that the
brilliant colours of butterflies, and of some few moths, have commonly been
acquired for the sake of protection. We have seen that their colours and
elegant patterns are arranged and exhibited as if for display. Hence I am
led to believe that the females prefer or are most excited by the more
brilliant males; for on any other supposition the males would, as far as we
can see, be ornamented to no purpose. We know that ants and certain
Lamellicorn beetles are capable of feeling an attachment for each other,
and that ants recognise their fellows after an interval of several months.
Hence there is no abstract improbability in the Lepidoptera, which probably
stand nearly or quite as high in the scale as these insects, having
sufficient mental capacity to admire bright colours. They certainly
discover flowers by colour. The Humming-bird Sphinx may often be seen to
swoop down from a distance on a bunch of flowers in the midst of green
foliage; and I have been assured by two persons abroad, that these moths
repeatedly visit flowers painted on the walls of a room, and vainly
endeavour to insert their proboscis into them. Fritz Muller informs me
that several kinds of butterflies in S. Brazil shew an unmistakable
preference for certain colours over others: he observed that they very
often visited the brilliant red flowers of five or six genera of plants,
but never the white or yellow flowering species of the same and other
genera, growing in the same garden; and I have received other accounts to
the same effect. As I hear from Mr. Doubleday, the common white butterfly
often flies down to a bit of paper on the ground, no doubt mistaking it for
one of its own species. Mr. Collingwood (22. 'Rambles of a Naturalist in
the Chinese Seas,' 1868, p. 182.) in speaking of the difficulty in
collecting certain butterflies in the Malay Archipelago, states that "a
dead specimen pinned upon a conspicuous twig will often arrest an insect of
the same species in its headlong flight, and bring it down within easy
reach of the net, especially if it be of the opposite sex."
The courtship of butterflies is, as before remarked, a prolonged affair.
The males sometimes fight together in rivalry; and many may be seen
pursuing or crowding round the same female. Unless, then, the females
prefer one male to another, the pairing must be left to mere chance, and
this does not appear probable. If, on the other band, the females
habitually, or even occasionally, prefer the more beautiful males, the
colours of the latter will have been rendered brighter by degrees, and will
have been transmitted to both sexes or to one sex, according to the law of
inheritance which has prevailed. The process of sexual selection will have
been much facilitated, if the conclusion can be trusted, arrived at from
various kinds of evidence in the supplement to the ninth chapter; namely,
that the males of many Lepidoptera, at least in the imago state, greatly
exceed the females in number.
Some facts, however, are opposed to the belief that female butterflies
prefer the more beautiful males; thus, as I have been assured by several
collectors, fresh females may frequently be seen paired with battered,
faded, or dingy males; but this is a circumstance which could hardly fail
often to follow from the males emerging from their cocoons earlier than the
females. With moths of the family of the Bombycidae, the sexes pair
immediately after assuming the imago state; for they cannot feed, owing to
the rudimentary condition of their mouths. The females, as several
entomologists have remarked to me, lie in an almost torpid state, and
appear not to evince the least choice in regard to their partners. This is
the case with the common silk-moth (B. mori), as I have been told by some
continental and English breeders. Dr. Wallace, who has had great
experience in breeding Bombyx cynthia, is convinced that the females evince
no choice or preference. He has kept above 300 of these moths together,
and has often found the most vigorous females mated with stunted males.
The reverse appears to occur seldom; for, as he believes, the more vigorous
males pass over the weakly females, and are attracted by those endowed with
most vitality. Nevertheless, the Bombycidae, though obscurely-coloured,
are often beautiful to our eyes from their elegant and mottled shades.
I have as yet only referred to the species in which the males are brighter
coloured than the females, and I have attributed their beauty to the
females for many generations having chosen and paired with the more
attractive males. But converse cases occur, though rarely, in which the
females are more brilliant than the males; and here, as I believe, the
males have selected the more beautiful females, and have thus slowly added
to their beauty. We do not know why in various classes of animals the
males of some few species have selected the more beautiful females instead
of having gladly accepted any female, as seems to be the general rule in
the animal kingdom: but if, contrary to what generally occurs with the
Lepidoptera, the females were much more numerous than the males, the latter
would be likely to pick out the more beautiful females. Mr. Butler shewed
me several species of Callidryas in the British Museum, in some of which
the females equalled, and in others greatly surpassed the males in beauty;
for the females alone have the borders of their wings suffused with crimson
and orange, and spotted with black. The plainer males of these species
closely resemble each other, shewing that here the females have been
modified; whereas in those cases, where the males are the more ornate, it
is these which have been modified, the females remaining closely alike.
In England we have some analogous cases, though not so marked. The females
alone of two species of Thecla have a bright-purple or orange patch on
their fore-wings. In Hipparchia the sexes do not differ much; but it is
the female of H. janira which has a conspicuous light-brown patch on her
wings; and the females of some of the other species are brighter coloured
than their males. Again, the females of Colias edusa and hyale have
"orange or yellow spots on the black marginal border, represented in the
males only by thin streaks"; and in Pieris it is the females which "are
ornamented with black spots on the fore-wings, and these are only partially
present in the males." Now the males of many butterflies are known to
support the females during their marriage flight; but in the species just
named it is the females which support the males; so that the part which the
two sexes play is reversed, as is their relative beauty. Throughout the
animal kingdom the males commonly take the more active share in wooing, and
their beauty seems to have been increased by the females having accepted
the more attractive individuals; but with these butterflies, the females
take the more active part in the final marriage ceremony, so that we may
suppose that they likewise do so in the wooing; and in this case we can
understand how it is that they have been rendered the more beautiful. Mr.
Meldola, from whom the foregoing statements have been taken, says in
conclusion: "Though I am not convinced of the action of sexual selection
in producing the colours of insects, it cannot be denied that these facts
are strikingly corroborative of Mr. Darwin's views." (23. 'Nature,' April
27, 1871, p. 508. Mr. Meldola quotes Donzel, in 'Soc. Ent. de France,'
1837, p. 77, on the flight of butterflies whilst pairing. See also Mr. G.
Fraser, in 'Nature,' April 20, 1871, p. 489, on the sexual differences of
several British butterflies.)
As sexual selection primarily depends on variability, a few words must be
added on this subject. In respect to colour there is no difficulty, for
any number of highly variable Lepidoptera could be named. One good
instance will suffice. Mr. Bates shewed me a whole series of specimens of
Papilio sesostris and P. childrenae; in the latter the males varied much in
the extent of the beautifully enamelled green patch on the fore-wings, and
in the size of the white mark, and of the splendid crimson stripe on the
hind-wings; so that there was a great contrast amongst the males between
the most and the least gaudy. The male of Papilio sesostris is much less
beautiful than of P. childrenae; and it likewise varies a little in the
size of the green patch on the fore-wings, and in the occasional appearance
of the small crimson stripe on the hind-wings, borrowed, as it would seem,
from its own female; for the females of this and of many other species in
the Aeneas group possess this crimson stripe. Hence between the brightest
specimens of P. sesostris and the dullest of P. childrenae, there was but a
small interval; and it was evident that as far as mere variability is
concerned, there would be no difficulty in permanently increasing the
beauty of either species by means of selection. The variability is here
almost confined to the male sex; but Mr. Wallace and Mr. Bates have shewn
(24. Wallace on the Papilionidae of the Malayan Region, in 'Transact.
Linn. Soc.' vol. xxv. 1865, pp. 8, 36. A striking case of a rare variety,
strictly intermediate between two other well-marked female varieties, is
given by Mr. Wallace. See also Mr. Bates, in 'Proc. Entomolog. Soc.' Nov.
19, 1866, p. xl.) that the females of some species are extremely variable,
the males being nearly constant. In a future chapter I shall have occasion
to shew that the beautiful eye-like spots, or ocelli, found on the wings of
many Lepidoptera, are eminently variable. I may here add that these ocelli
offer a difficulty on the theory of sexual selection; for though appearing
to us so ornamental, they are never present in one sex and absent in the
other, nor do they ever differ much in the two sexes. (25. Mr. Bates was
so kind as to lay this subject before the Entomological Society, and I have
received answers to this effect from several entomologists.) This fact is
at present inexplicable; but if it should hereafter be found that the
formation of an ocellus is due to some change in the tissues of the wings,
for instance, occurring at a very early period of development, we might
expect, from what we know of the laws of inheritance, that it would be
transmitted to both sexes, though arising and perfected in one sex alone.
On the whole, although many serious objections may be urged, it seems
probable that most of the brilliantly-coloured species of Lepidoptera owe
their colours to sexual selection, excepting in certain cases, presently to
be mentioned, in which conspicuous colours have been gained through mimicry
as a protection. From the ardour of the male throughout the animal
kingdom, he is generally willing to accept any female; and it is the female
which usually exerts a choice. Hence, if sexual selection has been
efficient with the Lepidoptera, the male, when the sexes differ, ought to
be the more brilliantly coloured, and this undoubtedly is the case. When
both sexes are brilliantly coloured and resemble each other, the characters
acquired by the males appear to have been transmitted to both. We are led
to this conclusion by cases, even within the same genus, of gradation from
an extraordinary amount of difference to identity in colour between the two
sexes.
But it may be asked whether the difference in colour between the sexes may
not be accounted for by other means besides sexual selection. Thus the
males and females of the same species of butterfly are in several cases
known (26. H.W. Bates, 'The Naturalist on the Amazons,' vol. ii. 1863, p.
228. A.R. Wallace, in 'Transactions, Linnean Society,' vol. xxv. 1865, p.
10.) to inhabit different stations, the former commonly basking in the
sunshine, the latter haunting gloomy forests. It is therefore possible
that different conditions of life may have acted directly on the two sexes;
but this is not probable (27. On this whole subject see 'The Variation of
Animals and Plants under Domestication,' 1868, vol. ii. chap. xxiii.) as in
the adult state they are exposed to different conditions during a very
short period; and the larvae of both are exposed to the same conditions.
Mr. Wallace believes that the difference between the sexes is due not so
much to the males having been modified, as to the females having in all or
almost all cases acquired dull colours for the sake of protection. It
seems to me, on the contrary, far more probable that it is the males which
have been chiefly modified through sexual selection, the females having
been comparatively little changed. We can thus understand how it is that
the females of allied species generally resemble one another so much more
closely than do the males. They thus shew us approximately the primordial
colouring of the parent-species of the group to which they belong. They
have, however, almost always been somewhat modified by the transfer to them
of some of the successive variations, through the accumulation of which the
males were rendered beautiful. But I do not wish to deny that the females
alone of some species may have been specially modified for protection. In
most cases the males and females of distinct species will have been exposed
during their prolonged larval state to different conditions, and may have
been thus affected; though with the males any slight change of colour thus
caused will generally have been masked by the brilliant tints gained
through sexual selection. When we treat of Birds, I shall have to discuss
the whole question, as to how far the differences in colour between the
sexes are due to the males having been modified through sexual selection
for ornamental purposes, or to the females having been modified through
natural selection for the sake of protection, so that I will here say but
little on the subject.
In all the cases in which the more common form of equal inheritance by both
sexes has prevailed, the selection of bright-coloured males would tend to
make the females bright-coloured; and the selection of dull-coloured
females would tend to make the males dull. If both processes were carried
on simultaneously, they would tend to counteract each other; and the final
result would depend on whether a greater number of females from being well
protected by obscure colours, or a greater number of males by being
brightly-coloured and thus finding partners, succeeded in leaving more
numerous offspring.
In order to account for the frequent transmission of characters to one sex
alone, Mr. Wallace expresses his belief that the more common form of equal
inheritance by both sexes can be changed through natural selection into
inheritance by one sex alone, but in favour of this view I can discover no
evidence. We know from what occurs under domestication that new characters
often appear, which from the first are transmitted to one sex alone; and by
the selection of such variations there would not be the slightest
difficulty in giving bright colours to the males alone, and at the same
time or subsequently, dull colours to the females alone. In this manner
the females of some butterflies and moths have, it is probable, been
rendered inconspicuous for the sake of protection, and widely different
from their males.
I am, however, unwilling without distinct evidence to admit that two
complex processes of selection, each requiring the transference of new
characters to one sex alone, have been carried on with a multitude of
species,--that the males have been rendered more brilliant by beating their
rivals, and the females more dull-coloured by having escaped from their
enemies. The male, for instance, of the common brimstone butterfly
(Gonepteryx), is of a far more intense yellow than the female, though she
is equally conspicuous; and it does not seem probable that she specially
acquired her pale tints as a protection, though it is probable that the
male acquired his bright colours as a sexual attraction. The female of
Anthocharis cardamines does not possess the beautiful orange wing-tips of
the male; consequently she closely resembles the white butterflies (Pieris)
so common in our gardens; but we have no evidence that this resemblance is
beneficial to her. As, on the other hand, she resembles both sexes of
several other species of the genus inhabiting various quarters of the
world, it is probable that she has simply retained to a large extent her
primordial colours.
Finally, as we have seen, various considerations lead to the conclusion
that with the greater number of brilliantly-coloured Lepidoptera it is the
male which has been chiefly modified through sexual selection; the amount
of difference between the sexes mostly depending on the form of inheritance
which has prevailed. Inheritance is governed by so many unknown laws or
conditions, that it seems to us to act in a capricious manner (28. The
'Variation of Animals and Plants under Domestication,' vol. ii. chap. xii.
p. 17.); and we can thus, to a certain extent, understand how it is that
with closely allied species the sexes either differ to an astonishing
degree, or are identical in colour. As all the successive steps in the
process of variation are necessarily transmitted through the female, a
greater or less number of such steps might readily become developed in her;
and thus we can understand the frequent gradations from an extreme
difference to none at all between the sexes of allied species. These cases
of gradation, it may be added, are much too common to favour the
supposition that we here see females actually undergoing the process of
transition and losing their brightness for the sake of protection; for we
have every reason to conclude that at any one time the greater number of
species are in a fixed condition.
MIMICRY.
This principle was first made clear in an admirable paper by Mr. Bates (29.
'Transact. Linn. Soc.' vol. xxiii. 1862, p. 495.), who thus threw a flood
of light on many obscure problems. It had previously been observed that
certain butterflies in S. America belonging to quite distinct families,
resembled the Heliconidae so closely in every stripe and shade of colour,
that they could not be distinguished save by an experienced entomologist.
As the Heliconidae are coloured in their usual manner, whilst the others
depart from the usual colouring of the groups to which they belong, it is
clear that the latter are the imitators, and the Heliconidae the imitated.
Mr. Bates further observed that the imitating species are comparatively
rare, whilst the imitated abound, and that the two sets live mingled
together. From the fact of the Heliconidae being conspicuous and beautiful
insects, yet so numerous in individuals and species, he concluded that they
must be protected from the attacks of enemies by some secretion or odour;
and this conclusion has now been amply confirmed (30. 'Proc. Entomological
Soc.' Dec. 3, 1866, p. xlv.), especially by Mr. Belt. Hence Mr. Bates
inferred that the butterflies which imitate the protected species have
acquired their present marvellously deceptive appearance through variation
and natural selection, in order to be mistaken for the protected kinds, and
thus to escape being devoured. No explanation is here attempted of the
brilliant colours of the imitated, but only of the imitating butterflies.
We must account for the colours of the former in the same general manner,
as in the cases previously discussed in this chapter. Since the
publication of Mr. Bates' paper, similar and equally striking facts have
been observed by Mr. Wallace in the Malayan region, by Mr. Trimen in South
Africa, and by Mr. Riley in the United States. (31. Wallace, 'Transact.
Linn. Soc.' vol. xxv. 1865 p. i.; also, 'Transact. Ent. Soc.' vol. iv. (3rd
series), 1867, p. 301. Trimen, 'Linn. Transact.' vol. xxvi. 1869, p. 497.
Riley, 'Third Annual Report on the Noxious Insects of Missouri,' 1871, pp.
163-168. This latter essay is valuable, as Mr. Riley here discusses all
the objections which have been raised against Mr. Bates's theory.)
As some writers have felt much difficulty in understanding how the first
steps in the process of mimicry could have been effected through natural
selection, it may be well to remark that the process probably commenced
long ago between forms not widely dissimilar in colour. In this case even
a slight variation would be beneficial, if it rendered the one species more
like the other; and afterwards the imitated species might be modified to an
extreme degree through sexual selection or other means, and if the changes
were gradual, the imitators might easily be led along the same track, until
they differed to an equally extreme degree from their original condition;
and they would thus ultimately assume an appearance or colouring wholly
unlike that of the other members of the group to which they belonged. It
should also be remembered that many species of Lepidoptera are liable to
considerable and abrupt variations in colour. A few instances have been
given in this chapter; and many more may be found in the papers of Mr.
Bates and Mr. Wallace.
With several species the sexes are alike, and imitate the two sexes of
another species. But Mr. Trimen gives, in the paper already referred to,
three cases in which the sexes of the imitated form differ from each other
in colour, and the sexes of the imitating form differ in a like manner.
Several cases have also been recorded where the females alone imitate
brilliantly-coloured and protected species, the males retaining "the normal
aspect of their immediate congeners." It is here obvious that the
successive variations by which the female has been modified have been
transmitted to her alone. It is, however, probable that some of the many
successive variations would have been transmitted to, and developed in, the
males had not such males been eliminated by being thus rendered less
attractive to the females; so that only those variations were preserved
which were from the first strictly limited in their transmission to the
female sex. We have a partial illustration of these remarks in a statement
by Mr. Belt (32. 'The Naturalist in Nicaragua,' 1874, p. 385.); that the
males of some of the Leptalides, which imitate protected species, still
retain in a concealed manner some of their original characters. Thus in
the males "the upper half of the lower wing is of a pure white, whilst all
the rest of the wings is barred and spotted with black, red and yellow,
like the species they mimic. The females have not this white patch, and
the males usually conceal it by covering it with the upper wing, so that I
cannot imagine its being of any other use to them than as an attraction in
courtship, when they exhibit it to the females, and thus gratify their
deep-seated preference for the normal colour of the Order to which the
Leptalides belong."
BRIGHT COLOURS OF CATERPILLARS.
Whilst reflecting on the beauty of many butterflies, it occurred to me that
some caterpillars were splendidly coloured; and as sexual selection could
not possibly have here acted, it appeared rash to attribute the beauty of
the mature insect to this agency, unless the bright colours of their larvae
could be somehow explained. In the first place, it may be observed that
the colours of caterpillars do not stand in any close correlation with
those of the mature insect. Secondly, their bright colours do not serve in
any ordinary manner as a protection. Mr. Bates informs me, as an instance
of this, that the most conspicuous caterpillar which he ever beheld (that
of a Sphinx) lived on the large green leaves of a tree on the open llanos
of South America; it was about four inches in length, transversely banded
with black and yellow, and with its head, legs, and tail of a bright red.
Hence it caught the eye of any one who passed by, even at the distance of
many yards, and no doubt that of every passing bird.
I then applied to Mr. Wallace, who has an innate genius for solving
difficulties. After some consideration he replied: "Most caterpillars
require protection, as may be inferred from some kinds being furnished with
spines or irritating hairs, and from many being coloured green like the
leaves on which they feed, or being curiously like the twigs of the trees
on which they live." Another instance of protection, furnished me by Mr.
J. Mansel Weale, may be added, namely, that there is a caterpillar of a
moth which lives on the mimosas in South Africa, and fabricates for itself
a case quite indistinguishable from the surrounding thorns. From such
considerations Mr. Wallace thought it probable that conspicuously coloured
caterpillars were protected by having a nauseous taste; but as their skin
is extremely tender, and as their intestines readily protrude from a wound,
a slight peck from the beak of a bird would be as fatal to them as if they
had been devoured. Hence, as Mr. Wallace remarks, "distastefulness alone
would be insufficient to protect a caterpillar unless some outward sign
indicated to its would-be destroyer that its prey was a disgusting morsel."
Under these circumstances it would be highly advantageous to a caterpillar
to be instantaneously and certainly recognised as unpalatable by all birds
and other animals. Thus the most gaudy colours would be serviceable, and
might have been gained by variation and the survival of the most easily-
recognised individuals.
This hypothesis appears at first sight very bold, but when it was brought
before the Entomological Society (33. 'Proceedings, Entomological
Society,' Dec. 3, 1866, p. xlv. and March 4, 1867, p. lxxx.) it was
supported by various statements; and Mr. J. Jenner Weir, who keeps a large
number of birds in an aviary, informs me that he has made many trials, and
finds no exception to the rule, that all caterpillars of nocturnal and
retiring habits with smooth skins, all of a green colour, and all which
imitate twigs, are greedily devoured by his birds. The hairy and spinose
kinds are invariably rejected, as were four conspicuously-coloured species.
When the birds rejected a caterpillar, they plainly shewed, by shaking
their heads, and cleansing their beaks, that they were disgusted by the
taste. (34. See Mr. J. Jenner Weir's paper on Insects and Insectivorous
Birds, in 'Transact. Ent. Soc.' 1869, p. 21; also Mr. Butler's paper, ibid.
p. 27. Mr. Riley has given analogous facts in the 'Third Annual Report on
the Noxious Insects of Missouri,' 1871, p. 148. Some opposed cases are,
however, given by Dr. Wallace and M. H. d'Orville; see 'Zoological Record,'
1869, p. 349.) Three conspicuous kinds of caterpillars and moths were also
given to some lizards and frogs, by Mr. A. Butler, and were rejected,
though other kinds were eagerly eaten. Thus the probability of Mr.
Wallace's view is confirmed, namely, that certain caterpillars have been
made conspicuous for their own good, so as to be easily recognised by their
enemies, on nearly the same principle that poisons are sold in coloured
bottles by druggists for the good of man. We cannot, however, at present
thus explain the elegant diversity in the colours of many caterpillars; but
any species which had at some former period acquired a dull, mottled, or
striped appearance, either in imitation of surrounding objects, or from the
direct action of climate, etc., almost certainly would not become uniform
in colour, when its tints were rendered intense and bright; for in order to
make a caterpillar merely conspicuous, there would be no selection in any
definite direction.
SUMMARY AND CONCLUDING REMARKS ON INSECTS.
Looking back to the several Orders, we see that the sexes often differ in
various characters, the meaning of which is not in the least understood.
The sexes, also, often differ in their organs of sense and means of
locomotion, so that the males may quickly discover and reach the females.
They differ still oftener in the males possessing diversified contrivances
for retaining the females when found. We are, however, here concerned only
in a secondary degree with sexual differences of these kinds.
In almost all the Orders, the males of some species, even of weak and
delicate kinds, are known to be highly pugnacious; and some few are
furnished with special weapons for fighting with their rivals. But the law
of battle does not prevail nearly so widely with insects as with the higher
animals. Hence it probably arises, that it is in only a few cases that the
males have been rendered larger and stronger than the females. On the
contrary, they are usually smaller, so that they may be developed within a
shorter time, to be ready in large numbers for the emergence of the
females.
In two families of the Homoptera and in three of the Orthoptera, the males
alone possess sound-producing organs in an efficient state. These are used
incessantly during the breeding-season, not only for calling the females,
but apparently for charming or exciting them in rivalry with other males.
No one who admits the agency of selection of any kind, will, after reading
the above discussion, dispute that these musical instruments have been
acquired through sexual selection. In four other Orders the members of one
sex, or more commonly of both sexes, are provided with organs for producing
various sounds, which apparently serve merely as call-notes. When both
sexes are thus provided, the individuals which were able to make the
loudest or most continuous noise would gain partners before those which
were less noisy, so that their organs have probably been gained through
sexual selection. It is instructive to reflect on the wonderful diversity
of the means for producing sound, possessed by the males alone, or by both
sexes, in no less than six Orders. We thus learn how effectual sexual
selection has been in leading to modifications which sometimes, as with the
Homoptera, relate to important parts of the organisation.
From the reasons assigned in the last chapter, it is probable that the
great horns possessed by the males of many Lamellicorn, and some other
beetles, have been acquired as ornaments. From the small size of insects,
we are apt to undervalue their appearance. If we could imagine a male
Chalcosoma (Fig. 16), with its polished bronzed coat of mail, and its vast
complex horns, magnified to the size of a horse, or even of a dog, it would
be one of the most imposing animals in the world.
The colouring of insects is a complex and obscure subject. When the male
differs slightly from the female, and neither are brilliantly-coloured, it
is probable that the sexes have varied in a slightly different manner, and
that the variations have been transmitted by each sex to the same without
any benefit or evil thus accruing. When the male is brilliantly-coloured
and differs conspicuously from the female, as with some dragon-flies and
many butterflies, it is probable that he owes his colours to sexual
selection; whilst the female has retained a primordial or very ancient type
of colouring, slightly modified by the agencies before explained. But in
some cases the female has apparently been made obscure by variations
transmitted to her alone, as a means of direct protection; and it is almost
certain that she has sometimes been made brilliant, so as to imitate other
protected species inhabiting the same district. When the sexes resemble
each other and both are obscurely coloured, there is no doubt that they
have been in a multitude of cases so coloured for the sake of protection.
So it is in some instances when both are brightly-coloured, for they thus
imitate protected species, or resemble surrounding objects such as flowers;
or they give notice to their enemies that they are unpalatable. In other
cases in which the sexes resemble each other and are both brilliant,
especially when the colours are arranged for display, we may conclude that
they have been gained by the male sex as an attraction, and have been
transferred to the female. We are more especially led to this conclusion
whenever the same type of coloration prevails throughout a whole group, and
we find that the males of some species differ widely in colour from the
females, whilst others differ slightly or not at all with intermediate
gradations connecting these extreme states.
In the same manner as bright colours have often been partially transferred
from the males to the females, so it has been with the extraordinary horns
of many Lamellicorn and some other beetles. So again, the sound-producing
organs proper to the males of the Homoptera and Orthoptera have generally
been transferred in a rudimentary, or even in a nearly perfect condition,
to the females; yet not sufficiently perfect to be of any use. It is also
an interesting fact, as bearing on sexual selection, that the stridulating
organs of certain male Orthoptera are not fully developed until the last
moult; and that the colours of certain male dragon-flies are not fully
developed until some little time after their emergence from the pupal
state, and when they are ready to breed.
Sexual selection implies that the more attractive individuals are preferred
by the opposite sex; and as with insects, when the sexes differ, it is the
male which, with some rare exceptions, is the more ornamented, and departs
more from the type to which the species belongs;--and as it is the male
which searches eagerly for the female, we must suppose that the females
habitually or occasionally prefer the more beautiful males, and that these
have thus acquired their beauty. That the females in most or all the
Orders would have the power of rejecting any particular male, is probable
from the many singular contrivances possessed by the males, such as great
jaws, adhesive cushions, spines, elongated legs, etc., for seizing the
female; for these contrivances show that there is some difficulty in the
act, so that her concurrence would seem necessary. Judging from what we
know of the perceptive powers and affections of various insects, there is
no antecedent improbability in sexual selection having come largely into
play; but we have as yet no direct evidence on this head, and some facts
are opposed to the belief. Nevertheless, when we see many males pursuing
the same female, we can hardly believe that the pairing is left to blind
chance--that the female exerts no choice, and is not influenced by the
gorgeous colours or other ornaments with which the male is decorated.
If we admit that the females of the Homoptera and Orthoptera appreciate the
musical tones of their male partners, and that the various instruments have
been perfected through sexual selection, there is little improbability in
the females of other insects appreciating beauty in form or colour, and
consequently in such characters having been thus gained by the males. But
from the circumstance of colour being so variable, and from its having been
so often modified for the sake of protection, it is difficult to decide in
how large a proportion of cases sexual selection has played a part. This
is more especially difficult in those Orders, such as Orthoptera,
Hymenoptera, and Coleoptera, in which the two sexes rarely differ much in
colour; for we are then left to mere analogy. With the Coleoptera,
however, as before remarked, it is in the great Lamellicorn group, placed
by some authors at the head of the Order, and in which we sometimes see a
mutual attachment between the sexes, that we find the males of some species
possessing weapons for sexual strife, others furnished with wonderful
horns, many with stridulating organs, and others ornamented with splendid
metallic tints. Hence it seems probable that all these characters have
been gained through the same means, namely sexual selection. With
butterflies we have the best evidence, as the males sometimes take pains to
display their beautiful colours; and we cannot believe that they would act
thus, unless the display was of use to them in their courtship.
When we treat of Birds, we shall see that they present in their secondary
sexual characters the closest analogy with insects. Thus, many male birds
are highly pugnacious, and some are furnished with special weapons for
fighting with their rivals. They possess organs which are used during the
breeding-season for producing vocal and instrumental music. They are
frequently ornamented with combs, horns, wattles and plumes of the most
diversified kinds, and are decorated with beautiful colours, all evidently
for the sake of display. We shall find that, as with insects, both sexes
in certain groups are equally beautiful, and are equally provided with
ornaments which are usually confined to the male sex. In other groups both
sexes are equally plain-coloured and unornamented. Lastly, in some few
anomalous cases, the females are more beautiful than the males. We shall
often find, in the same group of birds, every gradation from no difference
between the sexes, to an extreme difference. We shall see that female
birds, like female insects, often possess more or less plain traces or
rudiments of characters which properly belong to the males and are of use
only to them. The analogy, indeed, in all these respects between birds and
insects is curiously close. Whatever explanation applies to the one class
probably applies to the other; and this explanation, as we shall hereafter
attempt to shew in further detail, is sexual selection.
CHAPTER XII.
SECONDARY SEXUAL CHARACTERS OF FISHES, AMPHIBIANS, AND REPTILES.
FISHES: Courtship and battles of the males--Larger size of the females--
Males, bright colours and ornamental appendages; other strange characters--
Colours and appendages acquired by the males during the breeding-season
alone--Fishes with both sexes brilliantly coloured--Protective colours--The
less conspicuous colours of the female cannot be accounted for on the
principle of protection--Male fishes building nests, and taking charge of
the ova and young.
AMPHIBIANS: Differences in structure and colour between the sexes--Vocal
organs.
REPTILES: Chelonians--Crocodiles--Snakes, colours in some cases
protective--Lizards, battles of--Ornamental appendages--Strange differences
in structure between the sexes--Colours--Sexual differences almost as great
as with birds.
We have now arrived at the great sub-kingdom of the Vertebrata, and will
commence with the lowest class, that of fishes. The males of Plagiostomous
fishes (sharks, rays) and of Chimaeroid fishes are provided with claspers
which serve to retain the female, like the various structures possessed by
many of the lower animals. Besides the claspers, the males of many rays
have clusters of strong sharp spines on their heads, and several rows along
"the upper outer surface of their pectoral fins." These are present in the
males of some species, which have other parts of their bodies smooth. They
are only temporarily developed during the breeding-season; and Dr. Gunther
suspects that they are brought into action as prehensile organs by the
doubling inwards and downwards of the two sides of the body. It is a
remarkable fact that the females and not the males of some species, as of
Raia clavata, have their backs studded with large hook-formed spines. (1.
Yarrell's 'Hist. of British Fishes,' vol. ii. 1836, pp 417, 425, 436. Dr.
Gunther informs me that the spines in R. clavata are peculiar to the
female.)
The males alone of the capelin (Mallotus villosus, one of Salmonidae), are
provided with a ridge of closely-set, brush-like scales, by the aid of
which two males, one on each side, hold the female, whilst she runs with
great swiftness on the sandy beach, and there deposits her spawn. (2. The
'American Naturalist,' April 1871, p. 119.) The widely distinct
Monacanthus scopas presents a somewhat analogous structure. The male, as
Dr. Gunther informs me, has a cluster of stiff, straight spines, like those
of a comb, on the sides of the tail; and these in a specimen six inches
long were nearly one and a half inches in length; the female has in the
same place a cluster of bristles, which may be compared with those of a
tooth-brush. In another species, M. peronii, the male has a brush like
that possessed by the female of the last species, whilst the sides of the
tail in the female are smooth. In some other species of the same genus the
tail can be perceived to be a little roughened in the male and perfectly
smooth in the female; and lastly in others, both sexes have smooth sides.
The males of many fish fight for the possession of the females. Thus the
male stickleback (Gasterosteus leiurus) has been described as "mad with
delight," when the female comes out of her hiding-place and surveys the
nest which he has made for her. "He darts round her in every direction,
then to his accumulated materials for the nest, then back again in an
instant; and as she does not advance he endeavours to push her with his
snout, and then tries to pull her by the tail and side-spine to the nest."
(3. See Mr. R. Warington's interesting articles in 'Annals and Magazine of
Natural History,' October 1852, and November 1855.) The males are said to
be polygamists (4. Noel Humphreys, 'River Gardens,' 1857.); they are
extraordinarily bold and pugnacious, whilst "the females are quite
pacific." Their battles are at times desperate; "for these puny combatants
fasten tight on each other for several seconds, tumbling over and over
again until their strength appears completely exhausted." With the rough-
tailed stickleback (G. trachurus) the males whilst fighting swim round and
round each other, biting and endeavouring to pierce each other with their
raised lateral spines. The same writer adds (5. Loudon's 'Magazine of
Natural History,' vol. iii. 1830, p. 331.), "the bite of these little
furies is very severe. They also use their lateral spines with such fatal
effect, that I have seen one during a battle absolutely rip his opponent
quite open, so that he sank to the bottom and died." When a fish is
conquered, "his gallant bearing forsakes him; his gay colours fade away;
and he hides his disgrace among his peaceable companions, but is for some
time the constant object of his conqueror's persecution."
The male salmon is as pugnacious as the little stickleback; and so is the
male trout, as I hear from Dr. Gunther. Mr. Shaw saw a violent contest
between two male salmon which lasted the whole day; and Mr. R. Buist,
Superintendent of Fisheries, informs me that he has often watched from the
bridge at Perth the males driving away their rivals, whilst the females
were spawning. The males "are constantly fighting and tearing each other
on the spawning-beds, and many so injure each other as to cause the death
of numbers, many being seen swimming near the banks of the river in a state
of exhaustion, and apparently in a dying state." (6. The 'Field,' June
29, 1867. For Mr. Shaw's Statement, see 'Edinburgh Review,' 1843. Another
experienced observer (Scrope's 'Days of Salmon Fishing,' p. 60) remarks
that like the stag, the male would, if he could, keep all other males
away.) Mr. Buist informs me, that in June 1868, the keeper of the
Stormontfield breeding-ponds visited the northern Tyne and found about 300
dead salmon, all of which with one exception were males; and he was
convinced that they had lost their lives by fighting.
[Fig. 27. Head of male common salmon (Salmo salar) during the breeding-
season.
[This drawing, as well as all the others in the present chapter, have been
executed by the well-known artist, Mr. G. Ford, from specimens in the
British Museum, under the kind superintendence of Dr. Gunther.]
Fig. 28. Head of female salmon.]
The most curious point about the male salmon is that during the breeding-
season, besides a slight change in colour, "the lower jaw elongates, and a
cartilaginous projection turns upwards from the point, which, when the jaws
are closed, occupies a deep cavity between the intermaxillary bones of the
upper jaw." (7. Yarrell, 'History of British Fishes,' vol. ii. 1836, p.
10.) (Figs. 27 and 28.) In our salmon this change of structure lasts only
during the breeding-season; but in the Salmo lycaodon of N.W. America the
change, as Mr. J.K. Lord (8. 'The Naturalist in Vancouver's Island,' vol.
i. 1866, p. 54.) believes, is permanent, and best marked in the older males
which have previously ascended the rivers. In these old males the jaw
becomes developed into an immense hook-like projection, and the teeth grow
into regular fangs, often more than half an inch in length. With the
European salmon, according to Mr. Lloyd (9. 'Scandinavian Adventures,'
vol. i. 1854, pp. 100, 104.), the temporary hook-like structure serves to
strengthen and protect the jaws, when one male charges another with
wonderful violence; but the greatly developed teeth of the male American
salmon may be compared with the tusks of many male mammals, and they
indicate an offensive rather than a protective purpose.
The salmon is not the only fish in which the teeth differ in the two sexes;
as this is the case with many rays. In the thornback (Raia clavata) the
adult male has sharp, pointed teeth, directed backwards, whilst those of
the female are broad and flat, and form a pavement; so that these teeth
differ in the two sexes of the same species more than is usual in distinct
genera of the same family. The teeth of the male become sharp only when he
is adult: whilst young they are broad and flat like those of the female.
As so frequently occurs with secondary sexual characters, both sexes of
some species of rays (for instance R. batis), when adult, possess sharp
pointed teeth; and here a character, proper to and primarily gained by the
male, appears to have been transmitted to the offspring of both sexes. The
teeth are likewise pointed in both sexes of R. maculata, but only when
quite adult; the males acquiring them at an earlier age than the females.
We shall hereafter meet with analogous cases in certain birds, in which the
male acquires the plumage common to both sexes when adult, at a somewhat
earlier age than does the female. With other species of rays the males
even when old never possess sharp teeth, and consequently the adults of
both sexes are provided with broad, flat teeth like those of the young, and
like those of the mature females of the above-mentioned species. (10. See
Yarrell's account of the rays in his 'History of British Fishes,' vol. ii.
1836, p. 416, with an excellent figure, and pp. 422, 432.) As the rays are
bold, strong and voracious fish, we may suspect that the males require
their sharp teeth for fighting with their rivals; but as they possess many
parts modified and adapted for the prehension of the female, it is possible
that their teeth may be used for this purpose.
In regard to size, M. Carbonnier (11. As quoted in 'The Farmer,' 1868, p.
369.) maintains that the female of almost all fishes is larger than the
male; and Dr. Gunther does not know of a single instance in which the male
is actually larger than the female. With some Cyprinodonts the male is not
even half as large. As in many kinds of fishes the males habitually fight
together, it is surprising that they have not generally become larger and
stronger than the females through the effects of sexual selection. The
males suffer from their small size, for according to M. Carbonnier, they
are liable to be devoured by the females of their own species when
carnivorous, and no doubt by other species. Increased size must be in some
manner of more importance to the females, than strength and size are to the
males for fighting with other males; and this perhaps is to allow of the
production of a vast number of ova.
[Fig. 29. Callionymus lyra.
Upper figure, male;
lower figure, female.
N.B. The lower figure is more reduced than the upper.]
In many species the male alone is ornamented with bright colours; or these
are much brighter in the male than the female. The male, also, is
sometimes provided with appendages which appear to be of no more use to him
for the ordinary purposes of life, than are the tail feathers to the
peacock. I am indebted for most of the following facts to the kindness of
Dr. Gunther. There is reason to suspect that many tropical fishes differ
sexually in colour and structure; and there are some striking cases with
our British fishes. The male Callionymus lyra has been called the gemmeous
dragonet "from its brilliant gem-like colours." When fresh caught from the
sea the body is yellow of various shades, striped and spotted with vivid
blue on the head; the dorsal fins are pale brown with dark longitudinal
bands; the ventral, caudal, and anal fins being bluish-black. The female,
or sordid dragonet, was considered by Linnaeus, and by many subsequent
naturalists, as a distinct species; it is of a dingy reddish-brown, with
the dorsal fin brown and the other fins white. The sexes differ also in
the proportional size of the head and mouth, and in the position of the
eyes (12. I have drawn up this description from Yarrell's 'British
Fishes,' vol. i. 1836, pp. 261 and 266.); but the most striking difference
is the extraordinary elongation in the male (Fig. 29) of the dorsal fin.
Mr. W. Saville Kent remarks that this "singular appendage appears from my
observations of the species in confinement, to be subservient to the same
end as the wattles, crests, and other abnormal adjuncts of the male in
gallinaceous birds, for the purpose of fascinating their mates." (13.
'Nature,' July 1873, p. 264.) The young males resemble the adult females
in structure and colour. Throughout the genus Callionymus (14. 'Catalogue
of Acanth. Fishes in the British Museum,' by Dr. Gunther, 1861, pp. 138-
151.), the male is generally much more brightly spotted than the female,
and in several species, not only the dorsal, but the anal fin is much
elongated in the males.
The male of the Cottus scorpius, or sea-scorpion, is slenderer and smaller
than the female. There is also a great difference in colour between them.
It is difficult, as Mr. Lloyd (15. 'Game Birds of Sweden,' etc., 1867, p.
466.) remarks, "for any one, who has not seen this fish during the
spawning-season, when its hues are brightest, to conceive the admixture of
brilliant colours with which it, in other respects so ill-favoured, is at
that time adorned." Both sexes of the Labrus mixtus, although very
different in colour, are beautiful; the male being orange with bright blue
stripes, and the female bright red with some black spots on the back.
[Fig. 30. Xiphophorus Hellerii.
Upper figure, male;
lower figure, female.]
In the very distinct family of the Cyprinodontidae--inhabitants of the
fresh waters of foreign lands--the sexes sometimes differ much in various
characters. In the male of the Mollienesia petenensis (16. With respect
to this and the following species I am indebted to Dr. Gunther for
information: see also his paper on the 'Fishes of Central America,' in
'Transact. Zoological Soc.' vol. vi. 1868, p. 485.), the dorsal fin is
greatly developed and is marked with a row of large, round, ocellated,
bright-coloured spots; whilst the same fin in the female is smaller, of a
different shape, and marked only with irregularly curved brown spots. In
the male the basal margin of the anal fin is also a little produced and
dark coloured. In the male of an allied form, the Xiphophorus Hellerii
(Fig. 30), the inferior margin of the caudal fin is developed into a long
filament, which, as I hear from Dr. Gunther, is striped with bright
colours. This filament does not contain any muscles, and apparently cannot
be of any direct use to the fish. As in the case of the Callionymus, the
males whilst young resemble the adult females in colour and structure.
Sexual differences such as these may be strictly compared with those which
are so frequent with gallinaceous birds. (17. Dr. Gunther makes this
remark; 'Catalogue of Fishes in the British Museum,' vol. iii. 1861, p.
141.)
[Fig.31. Plecostomus barbatus.
Upper figure, head of male;
lower figure, female.]
In a siluroid fish, inhabiting the fresh waters of South America, the
Plecostomus barbatus (18. See Dr. Gunther on this genus, in 'Proceedings
of the Zoological Society,' 1868, p. 232.) (Fig. 31), the male has its
mouth and inter-operculum fringed with a beard of stiff hairs, of which the
female shows hardly a trace. These hairs are of the nature of scales. In
another species of the same genus, soft flexible tentacles project from the
front part of the head of the male, which are absent in the female. These
tentacles are prolongations of the true skin, and therefore are not
homologous with the stiff hairs of the former species; but it can hardly be
doubted that both serve the same purpose. What this purpose may be, it is
difficult to conjecture; ornament does not here seem probable, but we can
hardly suppose that stiff hairs and flexible filaments can be useful in any
ordinary way to the males alone. In that strange monster, the Chimaera
monstrosa, the male has a hook-shaped bone on the top of the head, directed
forwards, with its end rounded and covered with sharp spines; in the female
"this crown is altogether absent," but what its use may be to the male is
utterly unknown. (19. F. Buckland, in 'Land and Water,' July 1868, p.
377, with a figure. Many other cases could be added of structures peculiar
to the male, of which the uses are not known.)
The structures as yet referred to are permanent in the male after he has
arrived at maturity; but with some Blennies, and in another allied genus
(20. Dr. Gunther, 'Catalogue of Fishes,' vol. iii. pp. 221 and 240.), a
crest is developed on the head of the male only during the breeding-season,
and the body at the same time becomes more brightly-coloured. There can be
little doubt that this crest serves as a temporary sexual ornament, for the
female does not exhibit a trace of it. In other species of the same genus
both sexes possess a crest, and in at least one species neither sex is thus
provided. In many of the Chromidae, for instance in Geophagus and
especially in Cichla, the males, as I hear from Professor Agassiz (21. See
also 'A Journey in Brazil,' by Prof. and Mrs. Agassiz, 1868, p. 220.), have
a conspicuous protuberance on the forehead, which is wholly wanting in the
females and in the young males. Professor Agassiz adds, "I have often
observed these fishes at the time of spawning when the protuberance is
largest, and at other seasons when it is totally wanting, and the two sexes
shew no difference whatever in the outline of the profile of the head. I
never could ascertain that it subserves any special function, and the
Indians on the Amazon know nothing about its use." These protuberances
resemble, in their periodical appearance, the fleshy carbuncles on the
heads of certain birds; but whether they serve as ornaments must remain at
present doubtful.
I hear from Professor Agassiz and Dr. Gunther, that the males of those
fishes, which differ permanently in colour from the females, often become
more brilliant during the breeding-season. This is likewise the case with
a multitude of fishes, the sexes of which are identical in colour at all
other seasons of the year. The tench, roach, and perch may be given as
instances. The male salmon at this season is "marked on the cheeks with
orange-coloured stripes, which give it the appearance of a Labrus, and the
body partakes of a golden orange tinge. The females are dark in colour,
and are commonly called black-fish." (22. Yarrell, 'History of British
Fishes,' vol. ii. 1836, pp. 10, 12, 35.) An analogous and even greater
change takes place with the Salmo eriox or bull trout; the males of the
char (S. umbla) are likewise at this season rather brighter in colour than
the females. (23. W. Thompson, in 'Annals and Magazine of Natural
History,' vol. vi. 1841, p. 440.) The colours of the pike (Esox
reticulatus) of the United States, especially of the male, become, during
the breeding-season, exceedingly intense, brilliant, and iridescent. (24.
'The American Agriculturalist,' 1868, p. 100.) Another striking instance
out of many is afforded by the male stickleback (Gasterosteus leiurus),
which is described by Mr. Warington (25. 'Annals and Mag. of Nat. Hist.'
Oct. 1852.), as being then "beautiful beyond description." The back and
eyes of the female are simply brown, and the belly white. The eyes of the
male, on the other hand, are "of the most splendid green, having a metallic
lustre like the green feathers of some humming-birds. The throat and belly
are of a bright crimson, the back of an ashy-green, and the whole fish
appears as though it were somewhat translucent and glowed with an internal
incandescence." After the breeding season these colours all change, the
throat and belly become of a paler red, the back more green, and the
glowing tints subside.
With respect to the courtship of fishes, other cases have been observed
since the first edition of this book appeared, besides that already given
of the stickleback. Mr. W.S. Kent says that the male of the Labrus mixtus,
which, as we have seen, differs in colour from the female, makes "a deep
hollow in the sand of the tank, and then endeavours in the most persuasive
manner to induce a female of the same species to share it with him,
swimming backwards and forwards between her and the completed nest, and
plainly exhibiting the greatest anxiety for her to follow." The males of
Cantharus lineatus become, during the breeding-season, of deep leaden-
black; they then retire from the shoal, and excavate a hollow as a nest.
"Each male now mounts vigilant guard over his respective hollow, and
vigorously attacks and drives away any other fish of the same sex. Towards
his companions of the opposite sex his conduct is far different; many of
the latter are now distended with spawn, and these he endeavours by all the
means in his power to lure singly to his prepared hollow, and there to
deposit the myriad ova with which they are laden, which he then protects
and guards with the greatest care." (26. 'Nature,' May 1873, p. 25.)
A more striking case of courtship, as well as of display, by the males of a
Chinese Macropus has been given by M. Carbonnier, who carefully observed
these fishes under confinement. (27. 'Bulletin de la Societe d'Acclimat.'
Paris, July 1869, and Jan. 1870.) The males are most beautifully coloured,
more so than the females. During the breeding-season they contend for the
possession of the females; and, in the act of courtship, expand their fins,
which are spotted and ornamented with brightly coloured rays, in the same
manner, according to M. Carbonnier, as the peacock. They then also bound
about the females with much vivacity, and appear by "l'etalage de leurs
vives couleurs chercher a attirer l'attention des femelles, lesquelles ne
paraissaient indifferentes a ce manege, elles nageaient avec une molle
lenteur vers les males et semblaient se complaire dans leur voisinage."
After the male has won his bride, he makes a little disc of froth by
blowing air and mucus out of his mouth. He then collects the fertilised
ova, dropped by the female, in his mouth; and this caused M. Carbonnier
much alarm, as he thought that they were going to be devoured. But the
male soon deposits them in the disc of froth, afterwards guarding them,
repairing the froth, and taking care of the young when hatched. I mention
these particulars because, as we shall presently see, there are fishes, the
males of which hatch their eggs in their mouths; and those who do not
believe in the principle of gradual evolution might ask how could such a
habit have originated; but the difficulty is much diminished when we know
that there are fishes which thus collect and carry the eggs; for if delayed
by any cause in depositing them, the habit of hatching them in their mouths
might have been acquired.
To return to our more immediate subject. The case stands thus: female
fishes, as far as I can learn, never willingly spawn except in the presence
of the males; and the males never fertilise the ova except in the presence
of the females. The males fight for the possession of the females. In
many species, the males whilst young resemble the females in colour; but
when adult become much more brilliant, and retain their colours throughout
life. In other species the males become brighter than the females and
otherwise more highly ornamented, only during the season of love. The
males sedulously court the females, and in one case, as we have seen, take
pains in displaying their beauty before them. Can it be believed that they
would thus act to no purpose during their courtship? And this would be the
case, unless the females exert some choice and select those males which
please or excite them most. If the female exerts such choice, all the
above facts on the ornamentation of the males become at once intelligible
by the aid of sexual selection.
We have next to inquire whether this view of the bright colours of certain
male fishes having been acquired through sexual selection can, through the
law of the equal transmission of characters to both sexes, be extended to
those groups in which the males and females are brilliant in the same, or
nearly the same degree and manner. In such a genus as Labrus, which
includes some of the most splendid fishes in the world--for instance, the
Peacock Labrus (L. pavo), described (28. Bory Saint Vincent, in 'Dict.
Class. d'Hist. Nat.' tom. ix. 1826, p. 151.), with pardonable exaggeration,
as formed of polished scales of gold, encrusting lapis-lazuli, rubies,
sapphires, emeralds, and amethysts--we may, with much probability, accept
this belief; for we have seen that the sexes in at least one species of the
genus differ greatly in colour. With some fishes, as with many of the
lowest animals, splendid colours may be the direct result of the nature of
their tissues and of the surrounding conditions, without the aid of
selection of any kind. The gold-fish (Cyprinus auratus), judging from the
analogy of the golden variety of the common carp, is perhaps a case in
point, as it may owe its splendid colours to a single abrupt variation, due
to the conditions to which this fish has been subjected under confinement.
It is, however, more probable that these colours have been intensified
through artificial selection, as this species has been carefully bred in
China from a remote period. (29. Owing to some remarks on this subject,
made in my work 'On the Variation of Animals under Domestication,' Mr. W.F.
Mayers ('Chinese Notes and Queries,' Aug. 1868, p. 123) has searched the
ancient Chinese encyclopedias. He finds that gold-fish were first reared
in confinement during the Sung Dynasty, which commenced A.D. 960. In the
year 1129 these fishes abounded. In another place it is said that since
the year 1548 there has been "produced at Hangchow a variety called the
fire-fish, from its intensely red colour. It is universally admired, and
there is not a household where it is not cultivated, IN RIVALRY AS TO ITS
COLOUR, and as a source of profit.") Under natural conditions it does not
seem probable that beings so highly organised as fishes, and which live
under such complex relations, should become brilliantly coloured without
suffering some evil or receiving some benefit from so great a change, and
consequently without the intervention of natural selection.
What, then, are we to conclude in regard to the many fishes, both sexes of
which are splendidly coloured? Mr. Wallace (30. 'Westminster Review,'
July 1867, p. 7.) believes that the species which frequent reefs, where
corals and other brightly-coloured organisms abound, are brightly coloured
in order to escape detection by their enemies; but according to my
recollection they were thus rendered highly conspicuous. In the fresh-
waters of the tropics there are no brilliantly-coloured corals or other
organisms for the fishes to resemble; yet many species in the Amazons are
beautifully coloured, and many of the carnivorous Cyprinidae in India are
ornamented with "bright longitudinal lines of various tints." (31.
'Indian Cyprinidae,' by Mr. M'Clelland, 'Asiatic Researches,' vol. xix.
part ii. 1839, p. 230.) Mr. M'Clelland, in describing these fishes, goes
so far as to suppose that "the peculiar brilliancy of their colours" serves
as "a better mark for king-fishers, terns, and other birds which are
destined to keep the number of these fishes in check"; but at the present
day few naturalists will admit that any animal has been made conspicuous as
an aid to its own destruction. It is possible that certain fishes may have
been rendered conspicuous in order to warn birds and beasts of prey that
they were unpalatable, as explained when treating of caterpillars; but it
is not, I believe, known that any fish, at least any fresh-water fish, is
rejected from being distasteful to fish-devouring animals. On the whole,
the most probable view in regard to the fishes, of which both sexes are
brilliantly coloured, is that their colours were acquired by the males as a
sexual ornament, and were transferred equally, or nearly so, to the other
sex.
We have now to consider whether, when the male differs in a marked manner
from the female in colour or in other ornaments, he alone has been
modified, the variations being inherited by his male offspring alone; or
whether the female has been specially modified and rendered inconspicuous
for the sake of protection, such modifications being inherited only by the
females. It is impossible to doubt that colour has been gained by many
fishes as a protection: no one can examine the speckled upper surface of a
flounder, and overlook its resemblance to the sandy bed of the sea on which
it lives. Certain fishes, moreover, can through the action of the nervous
system change their colours in adaptation to surrounding objects, and that
within a short time. (32. G. Pouchet, 'L'Institut.' Nov. 1, 1871, p.
134.) One of the most striking instances ever recorded of an animal being
protected by its colour (as far as it can be judged of in preserved
specimens), as well as by its form, is that given by Dr. Gunther (33.
'Proc. Zoolog. Soc.' 1865, p. 327, pl. xiv. and xv.) of a pipe-fish, which,
with its reddish streaming filaments, is hardly distinguishable from the
sea-weed to which it clings with its prehensile tail. But the question now
under consideration is whether the females alone have been modified for
this object. We can see that one sex will not be modified through natural
selection for the sake of protection more than the other, supposing both to
vary, unless one sex is exposed for a longer period to danger, or has less
power of escaping from such danger than the other; and it does not appear
that with fishes the sexes differ in these respects. As far as there is
any difference, the males, from being generally smaller and from wandering
more about, are exposed to greater danger than the females; and yet, when
the sexes differ, the males are almost always the more conspicuously
coloured. The ova are fertilised immediately after being deposited; and
when this process lasts for several days, as in the case of the salmon (34.
Yarrell, 'British Fishes,' vol. ii. p. 11.), the female, during the whole
time, is attended by the male. After the ova are fertilised they are, in
most cases, left unprotected by both parents, so that the males and
females, as far as oviposition is concerned, are equally exposed to danger,
and both are equally important for the production of fertile ova;
consequently the more or less brightly-coloured individuals of either sex
would be equally liable to be destroyed or preserved, and both would have
an equal influence on the colours of their offspring.
Certain fishes, belonging to several families, make nests, and some of them
take care of their young when hatched. Both sexes of the bright coloured
Crenilabrus massa and melops work together in building their nests with
sea-weed, shells, etc. (35. According to the observations of M. Gerbe;
see Gunther's 'Record of Zoolog. Literature,' 1865, p. 194.) But the males
of certain fishes do all the work, and afterwards take exclusive charge of
the young. This is the case with the dull-coloured gobies (36. Cuvier,
'Regne Animal,' vol. ii. 1829, p. 242.), in which the sexes are not known
to differ in colour, and likewise with the sticklebacks (Gasterosteus), in
which the males become brilliantly coloured during the spawning season.
The male of the smooth-tailed stickleback (G. leiurus) performs the duties
of a nurse with exemplary care and vigilance during a long time, and is
continually employed in gently leading back the young to the nest, when
they stray too far. He courageously drives away all enemies including the
females of his own species. It would indeed be no small relief to the
male, if the female, after depositing her eggs, were immediately devoured
by some enemy, for he is forced incessantly to drive her from the nest.
(37. See Mr. Warington's most interesting description of the habits of the
Gasterosteus leiurus in 'Annals and Magazine of Nat. History,' November
1855.)
The males of certain other fishes inhabiting South America and Ceylon,
belonging to two distinct Orders, have the extraordinary habit of hatching
within their mouths, or branchial cavities, the eggs laid by the females.
(38. Prof. Wyman, in 'Proc. Boston Soc. of Nat. Hist.' Sept. 15, 1857.
Also Prof. Turner, in 'Journal of Anatomy and Physiology,' Nov. 1, 1866, p.
78. Dr. Gunther has likewise described other cases.) I am informed by
Professor Agassiz that the males of the Amazonian species which follow this
habit, "not only are generally brighter than the females, but the
difference is greater at the spawning-season than at any other time." The
species of Geophagus act in the same manner; and in this genus, a
conspicuous protuberance becomes developed on the forehead of the males
during the breeding-season. With the various species of Chromids, as
Professor Agassiz likewise informs me, sexual differences in colour may be
observed, "whether they lay their eggs in the water among aquatic plants,
or deposit them in holes, leaving them to come out without further care, or
build shallow nests in the river mud, over which they sit, as our Pomotis
does. It ought also to be observed that these sitters are among the
brightest species in their respective families; for instance, Hygrogonus is
bright green, with large black ocelli, encircled with the most brilliant
red." Whether with all the species of Chromids it is the male alone which
sits on the eggs is not known. It is, however, manifest that the fact of
the eggs being protected or unprotected by the parents, has had little or
no influence on the differences in colour between the sexes. It is further
manifest, in all the cases in which the males take exclusive charge of the
nests and young, that the destruction of the brighter-coloured males would
be far more influential on the character of the race, than the destruction
of the brighter-coloured females; for the death of the male during the
period of incubation or nursing would entail the death of the young, so
that they could not inherit his peculiarities; yet, in many of these very
cases the males are more conspicuously coloured than the females.
In most of the Lophobranchii (Pipe-fish, Hippocampi, etc.) the males have
either marsupial sacks or hemispherical depressions on the abdomen, in
which the ova laid by the female are hatched. The males also shew great
attachment to their young. (39. Yarrell, 'History of British Fishes,'
vol. ii. 1836, pp. 329, 338.) The sexes do not commonly differ much in
colour; but Dr. Gunther believes that the male Hippocampi are rather
brighter than the females. The genus Solenostoma, however, offers a
curious exceptional case (40. Dr. Gunther, since publishing an account of
this species in 'The Fishes of Zanzibar,' by Col. Playfair, 1866, p. 137,
has re-examined the specimens, and has given me the above information.),
for the female is much more vividly-coloured and spotted than the male, and
she alone has a marsupial sack and hatches the eggs; so that the female of
Solenostoma differs from all the other Lophobranchii in this latter
respect, and from almost all other fishes, in being more brightly-coloured
than the male. It is improbable that this remarkable double inversion of
character in the female should be an accidental coincidence. As the males
of several fishes, which take exclusive charge of the eggs and young, are
more brightly coloured than the females, and as here the female Solenostoma
takes the same charge and is brighter than the male, it might be argued
that the conspicuous colours of that sex which is the more important of the
two for the welfare of the offspring, must be in some manner protective.
But from the large number of fishes, of which the males are either
permanently or periodically brighter than the females, but whose life is
not at all more important for the welfare of the species than that of the
female, this view can hardly be maintained. When we treat of birds we
shall meet with analogous cases, where there has been a complete inversion
of the usual attributes of the two sexes, and we shall then give what
appears to be the probable explanation, namely, that the males have
selected the more attractive females, instead of the latter having
selected, in accordance with the usual rule throughout the animal kingdom,
the more attractive males.
On the whole we may conclude, that with most fishes, in which the sexes
differ in colour or in other ornamental characters, the males originally
varied, with their variations transmitted to the same sex, and accumulated
through sexual selection by attracting or exciting the females. In many
cases, however, such characters have been transferred, either partially or
completely, to the females. In other cases, again, both sexes have been
coloured alike for the sake of protection; but in no instance does it
appear that the female alone has had her colours or other characters
specially modified for this latter purpose.
The last point which need be noticed is that fishes are known to make
various noises, some of which are described as being musical. Dr. Dufosse,
who has especially attended to this subject, says that the sounds are
voluntarily produced in several ways by different fishes: by the friction
of the pharyngeal bones--by the vibration of certain muscles attached to
the swim bladder, which serves as a resounding board--and by the vibration
of the intrinsic muscles of the swim bladder. By this latter means the
Trigla produces pure and long-drawn sounds which range over nearly an
octave. But the most interesting case for us is that of two species of
Ophidium, in which the males alone are provided with a sound-producing
apparatus, consisting of small movable bones, with proper muscles, in
connection with the swim bladder. (41. 'Comptes-Rendus,' tom. xlvi. 1858,
p. 353; tom. xlvii. 1858, p. 916; tom. liv. 1862, p. 393. The noise made
by the Umbrinas (Sciaena aquila), is said by some authors to be more like
that of a flute or organ, than drumming: Dr. Zouteveen, in the Dutch
translation of this work (vol. ii. p. 36), gives some further particulars
on the sounds made by fishes.) The drumming of the Umbrinas in the
European seas is said to be audible from a depth of twenty fathoms; and the
fishermen of Rochelle assert "that the males alone make the noise during
the spawning-time; and that it is possible by imitating it, to take them
without bait." (42. The Rev. C. Kingsley, in 'Nature,' May 1870, p. 40.)
From this statement, and more especially from the case of Ophidium, it is
almost certain that in this, the lowest class of the Vertebrata, as with so
many insects and spiders, sound-producing instruments have, at least in
some cases, been developed through sexual selection, as a means for
bringing the sexes together.
AMPHIBIANS.
URODELA.
[Fig. 32. Triton cristatus (half natural size, from Bell's 'British
Reptiles').
Upper figure, male during the breeding season;
lower figure, female.]
I will begin with the tailed amphibians. The sexes of salamanders or newts
often differ much both in colour and structure. In some species prehensile
claws are developed on the fore-legs of the males during the breeding-
season: and at this season in the male Triton palmipes the hind-feet are
provided with a swimming-web, which is almost completely absorbed during
the winter; so that their feet then resemble those of the female. (43.
Bell, 'History of British Reptiles,' 2nd ed., 1849, pp. 156-159.) This
structure no doubt aids the male in his eager search and pursuit of the
female. Whilst courting her he rapidly vibrates the end of his tail. With
our common newts (Triton punctatus and cristatus) a deep, much indented
crest is developed along the back and tail of the male during the breeding-
season, which disappears during the winter. Mr. St. George Mivart informs
me that it is not furnished with muscles, and therefore cannot be used for
locomotion. As during the season of courtship it becomes edged with bright
colours, there can hardly be a doubt that it is a masculine ornament. In
many species the body presents strongly contrasted, though lurid tints, and
these become more vivid during the breeding-season. The male, for
instance, of our common little newt (Triton punctatus) is "brownish-grey
above, passing into yellow beneath, which in the spring becomes a rich
bright orange, marked everywhere with round dark spots." The edge of the
crest also is then tipped with bright red or violet. The female is usually
of a yellowish-brown colour with scattered brown dots, and the lower
surface is often quite plain. (44. Bell, 'History of British Reptiles,'
2nd ed., 1849, pp. 146, 151.) The young are obscurely tinted. The ova are
fertilised during the act of deposition, and are not subsequently tended by
either parent. We may therefore conclude that the males have acquired
their strongly-marked colours and ornamental appendages through sexual
selection; these being transmitted either to the male offspring alone, or
to both sexes.
ANURA OR BATRACHIA.
With many frogs and toads the colours evidently serve as a protection, such
as the bright green tints of tree frogs and the obscure mottled shades of
many terrestrial species. The most conspicuously-coloured toad which I
ever saw, the Phryniscus nigricans (45. 'Zoology of the Voyage of the
"Beagle,"' 1843. Bell, ibid. p. 49.), had the whole upper surface of the
body as black as ink, with the soles of the feet and parts of the abdomen
spotted with the brightest vermilion. It crawled about the bare sandy or
open grassy plains of La Plata under a scorching sun, and could not fail to
catch the eye of every passing creature. These colours are probably
beneficial by making this animal known to all birds of prey as a nauseous
mouthful.
In Nicaragua there is a little frog "dressed in a bright livery of red and
blue" which does not conceal itself like most other species, but hops about
during the daytime, and Mr. Belt says (46. 'The Naturalist in Nicaragua,'
1874, p. 321.) that as soon as he saw its happy sense of security, he felt
sure that it was uneatable. After several trials he succeeded in tempting
a young duck to snatch up a young one, but it was instantly rejected; and
the duck "went about jerking its head, as if trying to throw off some
unpleasant taste."
With respect to sexual differences of colour, Dr. Gunther does not know of
any striking instance either with frogs or toads; yet he can often
distinguish the male from the female by the tints of the former being a
little more intense. Nor does he know of any striking difference in
external structure between the sexes, excepting the prominences which
become developed during the breeding-season on the front legs of the male,
by which he is enabled to hold the female. (47. The male alone of the
Bufo sikimmensis (Dr. Anderson, 'Proc. Zoolog. Soc.' 1871, p. 204) has two
plate-like callosities on the thorax and certain rugosities on the fingers,
which perhaps subserve the same end as the above-mentioned prominences.)
It is surprising that these animals have not acquired more strongly-marked
sexual characters; for though cold-blooded their passions are strong. Dr.
Gunther informs me that he has several times found an unfortunate female
toad dead and smothered from having been so closely embraced by three or
four males. Frogs have been observed by Professor Hoffman in Giessen
fighting all day long during the breeding-season, and with so much violence
that one had its body ripped open.
Frogs and toads offer one interesting sexual difference, namely, in the
musical powers possessed by the males; but to speak of music, when applied
to the discordant and overwhelming sounds emitted by male bull-frogs and
some other species, seems, according to our taste, a singularly
inappropriate expression. Nevertheless, certain frogs sing in a decidedly
pleasing manner. Near Rio Janeiro I used often to sit in the evening to
listen to a number of little Hylae, perched on blades of grass close to the
water, which sent forth sweet chirping notes in harmony. The various
sounds are emitted chiefly by the males during the breeding-season, as in
the case of the croaking of our common frog. (48. Bell, 'History British
Reptiles,' 1849, p. 93.) In accordance with this fact the vocal organs of
the males are more highly-developed than those of the females. In some
genera the males alone are provided with sacs which open into the larynx.
(49. J. Bishop, in 'Todd's Cyclopaedia of Anatomy and Physiology,' vol.
iv. p. 1503.) For instance, in the edible frog (Rana esculenta) "the sacs
are peculiar to the males, and become, when filled with air in the act of
croaking, large globular bladders, standing out one on each side of the
head, near the corners of the mouth." The croak of the male is thus
rendered exceedingly powerful; whilst that of the female is only a slight
groaning noise. (50. Bell, ibid. pp. 112-114.) In the several genera of
the family the vocal organs differ considerably in structure, and their
development in all cases may be attributed to sexual selection.
REPTILES.
CHELONIA.
Tortoises and turtles do not offer well-marked sexual differences. In some
species, the tail of the male is longer than that of the female. In some,
the plastron or lower surface of the shell of the male is slightly concave
in relation to the back of the female. The male of the mud-turtle of the
United States (Chrysemys picta) has claws on its front feet twice as long
as those of the female; and these are used when the sexes unite. (51. Mr.
C.J. Maynard, 'The American Naturalist,' Dec. 1869, p. 555.) With the huge
tortoise of the Galapagos Islands (Testudo nigra) the males are said to
grow to a larger size than the females: during the pairing-season, and at
no other time, the male utters a hoarse bellowing noise, which can be heard
at the distance of more than a hundred yards; the female, on the other
hand, never uses her voice. (52. See my 'Journal of Researches during the
Voyage of the "Beagle,"' 1845, p. 384.)
With the Testudo elegans of India, it is said "that the combats of the
males may be heard at some distance, from the noise they produce in butting
against each other." (53. Dr. Gunther, 'Reptiles of British India,' 1864,
p. 7.)
CROCODILIA.
The sexes apparently do not differ in colour; nor do I know that the males
fight together, though this is probable, for some kinds make a prodigious
display before the females. Bartram (54. 'Travels through Carolina,'
etc., 1791, p. 128.) describes the male alligator as striving to win the
female by splashing and roaring in the midst of a lagoon, "swollen to an
extent ready to burst, with its head and tail lifted up, he springs or
twirls round on the surface of the water, like an Indian chief rehearsing
his feats of war." During the season of love, a musky odour is emitted by
the submaxiliary glands of the crocodile, and pervades their haunts. (55.
Owen, 'Anatomy of Vertebrates,' vol. i. 1866, p. 615.)
OPHIDIA.
Dr. Gunther informs me that the males are always smaller than the females,
and generally have longer and slenderer tails; but he knows of no other
difference in external structure. In regard to colour, be can almost
always distinguish the male from the female, by his more strongly-
pronounced tints; thus the black zigzag band on the back of the male
English viper is more distinctly defined than in the female. The
difference is much plainer in the rattle-snakes of N. America, the male of
which, as the keeper in the Zoological Gardens shewed me, can at once be
distinguished from the female by having more lurid yellow about its whole
body. In S. Africa the Bucephalus capensis presents an analogous
difference, for the female "is never so fully variegated with yellow on the
sides as the male." (56. Sir Andrew Smith, 'Zoology of S. Africa:
Reptilia,' 1849, pl. x.) The male of the Indian Dipsas cynodon, on the
other hand, is blackish-brown, with the belly partly black, whilst the
female is reddish or yellowish-olive, with the belly either uniform
yellowish or marbled with black. In the Tragops dispar of the same country
the male is bright green, and the female bronze-coloured. (57. Dr. A.
Gunther, 'Reptiles of British India,' Ray Soc., 1864, pp. 304, 308.) No
doubt the colours of some snakes are protective, as shewn by the green
tints of tree-snakes, and the various mottled shades of the species which
live in sandy places; but it is doubtful whether the colours of many kinds,
for instance of the common English snake and viper, serve to conceal them;
and this is still more doubtful with the many foreign species which are
coloured with extreme elegance. The colours of certain species are very
different in the adult and young states. (58. Dr. Stoliczka, 'Journal of
Asiatic Society of Bengal,' vol. xxxix, 1870, pp. 205, 211.)
During the breeding-season the anal scent-glands of snakes are in active
function (59. Owen, 'Anatomy of Vertebrates,' vol. i. 1866, p. 615.); and
so it is with the same glands in lizards, and as we have seen with the
submaxiliary glands of crocodiles. As the males of most animals search for
the females, these odoriferous glands probably serve to excite or charm the
female, rather than to guide her to the spot where the male may be found.
Male snakes, though appearing so sluggish, are amorous; for many have been
observed crowding round the same female, and even round her dead body.
They are not known to fight together from rivalry. Their intellectual
powers are higher than might have been anticipated. In the Zoological
Gardens they soon learn not to strike at the iron bar with which their
cages are cleaned; and Dr. Keen of Philadelphia informs me that some snakes
which he kept learned after four or five times to avoid a noose, with which
they were at first easily caught. An excellent observer in Ceylon, Mr. E.
Layard, saw (60. 'Rambles in Ceylon,' in 'Annals and Magazine of Natural
History,' 2nd series, vol. ix. 1852, p. 333.) a cobra thrust its head
through a narrow hole and swallow a toad. "With this encumbrance he could
not withdraw himself; finding this, he reluctantly disgorged the precious
morsel, which began to move off; this was too much for snake philosophy to
bear, and the toad was again seized, and again was the snake, after violent
efforts to escape, compelled to part with its prey. This time, however, a
lesson had been learnt, and the toad was seized by one leg, withdrawn, and
then swallowed in triumph."
The keeper in the Zoological Gardens is positive that certain snakes, for
instance Crotalus and Python, distinguish him from all other persons.
Cobras kept together in the same cage apparently feel some attachment
towards each other. (61. Dr. Gunther, 'Reptiles of British India,' 1864,
p. 340.)
It does not, however, follow because snakes have some reasoning power,
strong passions and mutual affection, that they should likewise be endowed
with sufficient taste to admire brilliant colours in their partners, so as
to lead to the adornment of the species through sexual selection.
Nevertheless, it is difficult to account in any other manner for the
extreme beauty of certain species; for instance, of the coral-snakes of S.
America, which are of a rich red with black and yellow transverse bands. I
well remember how much surprise I felt at the beauty of the first coral-
snake which I saw gliding across a path in Brazil. Snakes coloured in this
peculiar manner, as Mr. Wallace states on the authority of Dr. Gunther (62.
'Westminster Review,' July 1st, 1867, p. 32.), are found nowhere else in
the world except in S. America, and here no less than four genera occur.
One of these, Elaps, is venomous; a second and widely-distinct genus is
doubtfully venomous, and the two others are quite harmless. The species
belonging to these distinct genera inhabit the same districts, and are so
like each other that no one "but a naturalist would distinguish the
harmless from the poisonous kinds." Hence, as Mr. Wallace believes, the
innocuous kinds have probably acquired their colours as a protection, on
the principle of imitation; for they would naturally be thought dangerous
by their enemies. The cause, however, of the bright colours of the
venomous Elaps remains to be explained, and this may perhaps be sexual
selection.
Snakes produce other sounds besides hissing. The deadly Echis carinata has
on its sides some oblique rows of scales of a peculiar structure with
serrated edges; and when this snake is excited these scales are rubbed
against each other, which produces "a curious prolonged, almost hissing
sound." (63. Dr. Anderson, 'Proc. Zoolog. Soc.' 1871, p. 196.) With
respect to the rattling of the rattle-snake, we have at last some definite
information: for Professor Aughey states (64. The 'American Naturalist,'
1873, p. 85.), that on two occasions, being himself unseen, he watched from
a little distance a rattle-snake coiled up with head erect, which continued
to rattle at short intervals for half an hour: and at last he saw another
snake approach, and when they met they paired. Hence he is satisfied that
one of the uses of the rattle is to bring the sexes together.
Unfortunately he did not ascertain whether it was the male or the female
which remained stationary and called for the other. But it by no means
follows from the above fact that the rattle may not be of use to these
snakes in other ways, as a warning to animals which would otherwise attack
them. Nor can I quite disbelieve the several accounts which have appeared
of their thus paralysing their prey with fear. Some other snakes also make
a distinct noise by rapidly vibrating their tails against the surrounding
stalks of plants; and I have myself heard this in the case of a
Trigonocephalus in S. America.
LACERTILIA.
The males of some, probably of many kinds of lizards, fight together from
rivalry. Thus the arboreal Anolis cristatellus of S. America is extremely
pugnacious: "During the spring and early part of the summer, two adult
males rarely meet without a contest. On first seeing one another, they nod
their heads up and down three or four times, and at the same time expanding
the frill or pouch beneath the throat; their eyes glisten with rage, and
after waving their tails from side to side for a few seconds, as if to
gather energy, they dart at each other furiously, rolling over and over,
and holding firmly with their teeth. The conflict generally ends in one of
the combatants losing his tail, which is often devoured by the victor."
The male of this species is considerably larger than the female (65. Mr.
N.L. Austen kept these animals alive for a considerable time; see 'Land and
Water,' July 1867, p. 9.); and this, as far as Dr. Gunther has been able to
ascertain, is the general rule with lizards of all kinds. The male alone
of the Cyrtodactylus rubidus of the Andaman Islands possesses pre-anal
pores; and these pores, judging from analogy, probably serve to emit an
odour. (66. Stoliczka, 'Journal of the Asiatic Society of Bengal,' vol.
xxxiv. 1870, p. 166.)
[Fig.33. Sitana minor.
Male with the gular pouch expanded (from Gunther's 'Reptiles of India')']
The sexes often differ greatly in various external characters. The male of
the above-mentioned Anolis is furnished with a crest which runs along the
back and tail, and can be erected at pleasure; but of this crest the female
does not exhibit a trace. In the Indian Cophotis ceylanica, the female has
a dorsal crest, though much less developed than in the male; and so it is,
as Dr. Gunther informs me, with the females of many Iguanas, Chameleons,
and other lizards. In some species, however, the crest is equally
developed in both sexes, as in the Iguana tuberculata. In the genus
Sitana, the males alone are furnished with a large throat pouch (Fig. 33),
which can be folded up like a fan, and is coloured blue, black, and red;
but these splendid colours are exhibited only during the pairing-season.
The female does not possess even a rudiment of this appendage. In the
Anolis cristatellus, according to Mr. Austen, the throat pouch, which is
bright red marbled with yellow, is present in the female, though in a
rudimental condition. Again, in certain other lizards, both sexes are
equally well provided with throat pouches. Here we see with species
belonging to the same group, as in so many previous cases, the same
character either confined to the males, or more largely developed in them
than in the females, or again equally developed in both sexes. The little
lizards of the genus Draco, which glide through the air on their rib-
supported parachutes, and which in the beauty of their colours baffle
description, are furnished with skinny appendages to the throat "like the
wattles of gallinaceous birds." These become erected when the animal is
excited. They occur in both sexes, but are best developed when the male
arrives at maturity, at which age the middle appendage is sometimes twice
as long as the head. Most of the species likewise have a low crest running
along the neck; and this is much more developed in the full-grown males
than in the females or young males. (67. All the foregoing statements and
quotations, in regard to Cophotis, Sitana and Draco, as well as the
following facts in regard to Ceratophora and Chamaeleon, are from Dr.
Gunther himself, or from his magnificent work on the 'Reptiles of British
India,' Ray Soc., 1864, pp. 122, 130, 135.)
A Chinese species is said to live in pairs during the spring; "and if one
is caught, the other falls from the tree to the ground, and allows itself
to be captured with impunity"--I presume from despair. (68. Mr. Swinhoe,
'Proc. Zoolog. Soc.' 1870, p. 240.)
[Fig. 34. Ceratophora Stoddartii.
Upper figure;
lower figure, female.]
There are other and much more remarkable differences between the sexes of
certain lizards. The male of Ceratophora aspera bears on the extremity of
his snout an appendage half as long as the head. It is cylindrical,
covered with scales, flexible, and apparently capable of erection: in the
female it is quite rudimental. In a second species of the same genus a
terminal scale forms a minute horn on the summit of the flexible appendage;
and in a third species (C. Stoddartii, fig. 34) the whole appendage is
converted into a horn, which is usually of a white colour, but assumes a
purplish tint when the animal is excited. In the adult male of this latter
species the horn is half an inch in length, but it is of quite minute size
in the female and in the young. These appendages, as Dr. Gunther has
remarked to me, may be compared with the combs of gallinaceous birds, and
apparently serve as ornaments.
[Fig. 35. Chamaeleo bifurcus.
Upper figure, male;
lower figure, female.
Fig. 36. Chamaeleo Owenii.
Upper figure, male;
lower figure, female.]
In the genus Chamaeleon we come to the acme of difference between the
sexes. The upper part of the skull of the male C. bifurcus (Fig. 35), an
inhabitant of Madagascar, is produced into two great, solid, bony
projections, covered with scales like the rest of the head; and of this
wonderful modification of structure the female exhibits only a rudiment.
Again, in Chamaeleo Owenii (Fig. 36), from the West Coast of Africa, the
male bears on his snout and forehead three curious horns, of which the
female has not a trace. These horns consist of an excrescence of bone
covered with a smooth sheath, forming part of the general integuments of
the body, so that they are identical in structure with those of a bull,
goat, or other sheath-horned ruminant. Although the three horns differ so
much in appearance from the two great prolongations of the skull in C.
bifurcus, we can hardly doubt that they serve the same general purpose in
the economy of these two animals. The first conjecture, which will occur
to every one, is that they are used by the males for fighting together; and
as these animals are very quarrelsome (69. Dr. Buchholz, 'Monatsbericht K.
Preuss. Akad.' Jan. 1874, p. 78.), this is probably a correct view. Mr.
T.W. Wood also informs me that he once watched two individuals of C.
pumilus fighting violently on the branch of a tree; they flung their heads
about and tried to bite each other; they then rested for a time and
afterwards continued their battle.
With many lizards the sexes differ slightly in colour, the tints and
stripes of the males being brighter and more distinctly defined than in the
females. This, for instance, is the case with the above Cophotis and with
the Acanthodactylus capensis of S. Africa. In a Cordylus of the latter
country, the male is either much redder or greener than the female. In the
Indian Calotes nigrilabris there is a still greater difference; the lips
also of the male are black, whilst those of the female are green. In our
common little viviparous lizard (Zootoca vivipara) "the under side of the
body and base of the tail in the male are bright orange, spotted with
black; in the female these parts are pale-greyish-green without spots."
(70. Bell, 'History of British Reptiles,' 2nd ed., 1849, p. 40.) We have
seen that the males alone of Sitana possess a throat-pouch; and this is
splendidly tinted with blue, black, and red. In the Proctotretus tenuis of
Chile the male alone is marked with spots of blue, green, and coppery-red.
(71. For Proctotretus, see 'Zoology of the Voyage of the "Beagle";
Reptiles,' by Mr. Bell, p. 8. For the Lizards of S. Africa, see 'Zoology
of S. Africa: Reptiles,' by Sir Andrew Smith, pl. 25 and 39. For the
Indian Calotes, see 'Reptiles of British India,' by Dr. Gunther, p. 143.)
In many cases the males retain the same colours throughout the year, but in
others they become much brighter during the breeding-season; I may give as
an additional instance the Calotes maria, which at this season has a bright
red head, the rest of the body being green. (72. Gunther in 'Proceedings,
Zoological Society,' 1870, p. 778, with a coloured figure.)
Both sexes of many species are beautifully coloured exactly alike; and
there is no reason to suppose that such colours are protective. No doubt
with the bright green kinds which live in the midst of vegetation, this
colour serves to conceal them; and in N. Patagonia I saw a lizard
(Proctotretus multimaculatus) which, when frightened, flattened its body,
closed its eyes, and then from its mottled tints was hardly distinguishable
from the surrounding sand. But the bright colours with which so many
lizards are ornamented, as well as their various curious appendages, were
probably acquired by the males as an attraction, and then transmitted
either to their male offspring alone, or to both sexes. Sexual selection,
indeed, seems to have played almost as important a part with reptiles as
with birds; and the less conspicuous colours of the females in comparison
with the males cannot be accounted for, as Mr. Wallace believes to be the
case with birds, by the greater exposure of the females to danger during
incubation.
CHAPTER XIII.
SECONDARY SEXUAL CHARACTERS OF BIRDS.
Sexual differences--Law of battle--Special weapons--Vocal organs--
Instrumental music--Love-antics and dances--Decorations, permanent and
seasonal--Double and single annual moults--Display of ornaments by the
males.
Secondary sexual characters are more diversified and conspicuous in birds,
though not perhaps entailing more important changes of structure, than in
any other class of animals. I shall, therefore, treat the subject at
considerable length. Male birds sometimes, though rarely, possess special
weapons for fighting with each other. They charm the female by vocal or
instrumental music of the most varied kinds. They are ornamented by all
sorts of combs, wattles, protuberances, horns, air-distended sacks, top-
knots, naked shafts, plumes and lengthened feathers gracefully springing
from all parts of the body. The beak and naked skin about the head, and
the feathers, are often gorgeously coloured. The males sometimes pay their
court by dancing, or by fantastic antics performed either on the ground or
in the air. In one instance, at least, the male emits a musky odour, which
we may suppose serves to charm or excite the female; for that excellent
observer, Mr. Ramsay (1. 'Ibis,' vol. iii. (new series), 1867, p. 414.),
says of the Australian musk-duck (Biziura lobata) that "the smell which the
male emits during the summer months is confined to that sex, and in some
individuals is retained throughout the year; I have never, even in the
breeding-season, shot a female which had any smell of musk." So powerful
is this odour during the pairing-season, that it can be detected long
before the bird can be seen. (2. Gould, 'Handbook of the Birds of
Australia,' 1865, vol. ii. p. 383.) On the whole, birds appear to be the
most aesthetic of all animals, excepting of course man, and they have
nearly the same taste for the beautiful as we have. This is shewn by our
enjoyment of the singing of birds, and by our women, both civilised and
savage, decking their heads with borrowed plumes, and using gems which are
hardly more brilliantly coloured than the naked skin and wattles of certain
birds. In man, however, when cultivated, the sense of beauty is manifestly
a far more complex feeling, and is associated with various intellectual
ideas.
Before treating of the sexual characters with which we are here more
particularly concerned, I may just allude to certain differences between
the sexes which apparently depend on differences in their habits of life;
for such cases, though common in the lower, are rare in the higher classes.
Two humming-birds belonging to the genus Eustephanus, which inhabit the
island of Juan Fernandez, were long thought to be specifically distinct,
but are now known, as Mr. Gould informs me, to be the male and female of
the same species, and they differ slightly in the form of the beak. In
another genus of humming-birds (Grypus), the beak of the male is serrated
along the margin and hooked at the extremity, thus differing much from that
of the female. In the Neomorpha of New Zealand, there is, as we have seen,
a still wider difference in the form of the beak in relation to the manner
of feeding of the two sexes. Something of the same kind has been observed
with the goldfinch (Carduelis elegans), for I am assured by Mr. J. Jenner
Weir that the bird-catchers can distinguish the males by their slightly
longer beaks. The flocks of males are often found feeding on the seeds of
the teazle (Dipsacus), which they can reach with their elongated beaks,
whilst the females more commonly feed on the seeds of the betony or
Scrophularia. With a slight difference of this kind as a foundation, we
can see how the beaks of the two sexes might be made to differ greatly
through natural selection. In some of the above cases, however, it is
possible that the beaks of the males may have been first modified in
relation to their contests with other males; and that this afterwards led
to slightly changed habits of life.
LAW OF BATTLE.
Almost all male birds are extremely pugnacious, using their beaks, wings,
and legs for fighting together. We see this every spring with our robins
and sparrows. The smallest of all birds, namely the humming-bird, is one
of the most quarrelsome. Mr. Gosse (3. Quoted by Mr. Gould, 'Introduction
to the Trochilidae,' 1861, page 29.) describes a battle in which a pair
seized hold of each other's beaks, and whirled round and round, till they
almost fell to the ground; and M. Montes de Oca, in speaking or another
genus of humming-bird, says that two males rarely meet without a fierce
aerial encounter: when kept in cages "their fighting has mostly ended in
the splitting of the tongue of one of the two, which then surely dies from
being unable to feed." (4. Gould, ibid. p. 52.) With waders, the males
of the common water-hen (Gallinula chloropus) "when pairing, fight
violently for the females: they stand nearly upright in the water and
strike with their feet." Two were seen to be thus engaged for half an
hour, until one got hold of the head of the other, which would have been
killed had not the observer interfered; the female all the time looking on
as a quiet spectator. (5. W. Thompson, 'Natural History of Ireland:
Birds,' vol. ii. 1850, p. 327.) Mr. Blyth informs me that the males of an
allied bird (Gallicrex cristatus) are a third larger than the females, and
are so pugnacious during the breeding-season that they are kept by the
natives of Eastern Bengal for the sake of fighting. Various other birds
are kept in India for the same purpose, for instance, the bulbuls
(Pycnonotus hoemorrhous) which "fight with great spirit." (6. Jerdon,
'Birds of India,' 1863, vol. ii. p. 96.)
[Fig. 37. The Ruff or Machetes pugnax (from Brehm's 'Thierleben').]
The polygamous ruff (Machetes pugnax, Fig. 37) is notorious for his extreme
pugnacity; and in the spring, the males, which are considerably larger than
the females, congregate day after day at a particular spot, where the
females propose to lay their eggs. The fowlers discover these spots by the
turf being trampled somewhat bare. Here they fight very much like game-
cocks, seizing each other with their beaks and striking with their wings.
The great ruff of feathers round the neck is then erected, and according to
Col. Montagu "sweeps the ground as a shield to defend the more tender
parts"; and this is the only instance known to me in the case of birds of
any structure serving as a shield. The ruff of feathers, however, from its
varied and rich colours probably serves in chief part as an ornament. Like
most pugnacious birds, they seem always ready to fight, and when closely
confined, often kill each other; but Montagu observed that their pugnacity
becomes greater during the spring, when the long feathers on their necks
are fully developed; and at this period the least movement by any one bird
provokes a general battle. (7. Macgillivray, 'History of British Birds,'
vol. iv. 1852, pp. 177-181.) Of the pugnacity of web-footed birds, two
instances will suffice: in Guiana "bloody fights occur during the
breeding-season between the males of the wild musk-duck (Cairina moschata);
and where these fights have occurred the river is covered for some distance
with feathers." (8. Sir R. Schomburgk, in 'Journal of Royal Geographic
Society,' vol. xiii. 1843, p. 31.) Birds which seem ill-adapted for
fighting engage in fierce conflicts; thus the stronger males of the pelican
drive away the weaker ones, snapping with their huge beaks and giving heavy
blows with their wings. Male snipe fight together, "tugging and pushing
each other with their bills in the most curious manner imaginable." Some
few birds are believed never to fight; this is the case, according to
Audubon, with one of the woodpeckers of the United States (Picu sauratus),
although "the hens are followed by even half a dozen of their gay suitors."
(9. 'Ornithological Biography,' vol. i. p. 191. For pelicans and snipes,
see vol. iii. pp. 138, 477.)
The males of many birds are larger than the females, and this no doubt is
the result of the advantage gained by the larger and stronger males over
their rivals during many generations. The difference in size between the
two sexes is carried to an extreme point in several Australian species;
thus the male musk-duck (Biziura), and the male Cincloramphus cruralis
(allied to our pipits) are by measurement actually twice as large as their
respective females. (10. Gould, 'Handbook of Birds of Australia,' vol. i.
p. 395; vol. ii. p. 383.) With many other birds the females are larger
than the males; and, as formerly remarked, the explanation often given,
namely, that the females have most of the work in feeding their young, will
not suffice. In some few cases, as we shall hereafter see, the females
apparently have acquired their greater size and strength for the sake of
conquering other females and obtaining possession of the males.
The males of many gallinaceous birds, especially of the polygamous kinds,
are furnished with special weapons for fighting with their rivals, namely
spurs, which can be used with fearful effect. It has been recorded by a
trustworthy writer (11. Mr. Hewitt, in the 'Poultry Book' by Tegetmeier,
1866, p. 137.) that in Derbyshire a kite struck at a game-hen accompanied
by her chickens, when the cock rushed to the rescue, and drove his spur
right through the eye and skull of the aggressor. The spur was with
difficulty drawn from the skull, and as the kite, though dead, retained his
grasp, the two birds were firmly locked together; but the cock when
disentangled was very little injured. The invincible courage of the game-
cock is notorious: a gentleman who long ago witnessed the brutal scene,
told me that a bird had both its legs broken by some accident in the
cockpit, and the owner laid a wager that if the legs could be spliced so
that the bird could stand upright, he would continue fighting. This was
effected on the spot, and the bird fought with undaunted courage until he
received his death-stroke. In Ceylon a closely allied, wild species, the
Gallus Stanleyi, is known to fight desperately "in defence of his
seraglio," so that one of the combatants is frequently found dead. (12.
Layard, 'Annals and Magazine of Natural History,' vol. xiv. 1854, p. 63.)
An Indian partridge (Ortygornis gularis), the male of which is furnished
with strong and sharp spurs, is so quarrelsome "that the scars of former
fights disfigure the breast of almost every bird you kill." (13. Jerdon,
'Birds of India,' vol. iii. p. 574.)
The males of almost all gallinaceous birds, even those which are not
furnished with spurs, engage during the breeding-season in fierce
conflicts. The Capercailzie and Black-cock (Tetrao urogallus and T.
tetrix), which are both polygamists, have regular appointed places, where
during many weeks they congregate in numbers to fight together and to
display their charms before the females. Dr. W. Kovalevsky informs me that
in Russia he has seen the snow all bloody on the arenas where the
capercailzie have fought; and the black-cocks "make the feathers fly in
every direction," when several "engage in a battle royal." The elder Brehm
gives a curious account of the Balz, as the love-dances and love-songs of
the Black-cock are called in Germany. The bird utters almost continuously
the strangest noises: "he holds his tail up and spreads it out like a fan,
he lifts up his head and neck with all the feathers erect, and stretches
his wings from the body. Then he takes a few jumps in different
directions, sometimes in a circle, and presses the under part of his beak
so hard against the ground that the chin feathers are rubbed off. During
these movements he beats his wings and turns round and round. The more
ardent he grows the more lively he becomes, until at last the bird appears
like a frantic creature." At such times the black-cocks are so absorbed
that they become almost blind and deaf, but less so than the capercailzie:
hence bird after bird may be shot on the same spot, or even caught by the
hand. After performing these antics the males begin to fight: and the
same black-cock, in order to prove his strength over several antagonists,
will visit in the course of one morning several Balz-places, which remain
the same during successive years. (14. Brehm, 'Thierleben,' 1867, B. iv.
s. 351. Some of the foregoing statements are taken from L. Lloyd, 'The
Game Birds of Sweden,' etc., 1867, p. 79.)
The peacock with his long train appears more like a dandy than a warrior,
but he sometimes engages in fierce contests: the Rev. W. Darwin Fox
informs me that at some little distance from Chester two peacocks became so
excited whilst fighting, that they flew over the whole city, still engaged,
until they alighted on the top of St. John's tower.
The spur, in those gallinaceous birds which are thus provided, is generally
single; but Polyplectron (Fig. 51) has two or more on each leg; and one of
the Blood-pheasants (Ithaginis cruentus) has been seen with five spurs.
The spurs are generally confined to the male, being represented by mere
knobs or rudiments in the female; but the females of the Java peacock (Pavo
muticus) and, as I am informed by Mr. Blyth, of the small fire-backed
pheasant (Euplocamus erythrophthalmus) possess spurs. In Galloperdix it is
usual for the males to have two spurs, and for the females to have only one
on each leg. (15. Jerdon, 'Birds of India': on Ithaginis, vol. iii. p.
523; on Galloperdix, p. 541.) Hence spurs may be considered as a masculine
structure, which has been occasionally more or less transferred to the
females. Like most other secondary sexual characters, the spurs are highly
variable, both in number and development, in the same species.
[Fig.38. Palamedea cornuta (from Brehm), shewing the double wing-spurs,
and the filament on the head.]
Various birds have spurs on their wings. But the Egyptian goose
(Chenalopex aegyptiacus) has only "bare obtuse knobs," and these probably
shew us the first steps by which true spurs have been developed in other
species. In the spur-winged goose, Plectropterus gambensis, the males have
much larger spurs than the females; and they use them, as I am informed by
Mr. Bartlett, in fighting together, so that, in this case, the wing-spurs
serve as sexual weapons; but according to Livingstone, they are chiefly
used in the defence of the young. The Palamedea (Fig. 38) is armed with a
pair of spurs on each wing; and these are such formidable weapons that a
single blow has been known to drive a dog howling away. But it does not
appear that the spurs in this case, or in that of some of the spur-winged
rails, are larger in the male than in the female. (16. For the Egyptian
goose, see Macgillivray, 'British Birds,' vol. iv. p. 639. For
Plectropterus, Livingstone's 'Travels,' p. 254. For Palamedea, Brehm's
'Thierleben,' B. iv. s. 740. See also on this bird Azara, 'Voyages dans
l'Amerique merid.' tom. iv. 1809, pp. 179, 253.) In certain plovers,
however, the wing-spurs must be considered as a sexual character. Thus in
the male of our common peewit (Vanellus cristatus) the tubercle on the
shoulder of the wing becomes more prominent during the breeding-season, and
the males fight together. In some species of Lobivanellus a similar
tubercle becomes developed during the breeding-season "into a short horny
spur." In the Australian L. lobatus both sexes have spurs, but these are
much larger in the males than in the females. In an allied bird, the
Hoplopterus armatus, the spurs do not increase in size during the breeding-
season; but these birds have been seen in Egypt to fight together, in the
same manner as our peewits, by turning suddenly in the air and striking
sideways at each other, sometimes with fatal results. Thus also they drive
away other enemies. (17. See, on our peewit, Mr. R. Carr in 'Land and
Water,' Aug. 8th, 1868, p. 46. In regard to Lobivanellus, see Jerdon's
'Birds of India,' vol. iii. p. 647, and Gould's 'Handbook of Birds of
Australia,' vol. ii. p. 220. For the Hoplopterus, see Mr. Allen in the
'Ibis,' vol. v. 1863, p. 156.)
The season of love is that of battle; but the males of some birds, as of
the game-fowl and ruff, and even the young males of the wild turkey and
grouse (18. Audubon, 'Ornithological Biography,' vol. ii. p. 492; vol. i.
pp. 4-13.), are ready to fight whenever they meet. The presence of the
female is the teterrima belli causa. The Bengali baboos make the pretty
little males of the amadavat (Estrelda amandava) fight together by placing
three small cages in a row, with a female in the middle; after a little
time the two males are turned loose, and immediately a desperate battle
ensues. (19. Mr. Blyth, 'Land and Water,' 1867, p. 212.) When many males
congregate at the same appointed spot and fight together, as in the case of
grouse and various other birds, they are generally attended by the females
(20. Richardson on Tetrao umbellus, 'Fauna Bor. Amer.: Birds,' 1831, p.
343. L. Lloyd, 'Game Birds of Sweden,' 1867, pp. 22, 79, on the
capercailzie and black-cock. Brehm, however, asserts ('Thierleben,' B. iv.
s. 352) that in Germany the grey-hens do not generally attend the Balzen of
the black-cocks, but this is an exception to the common rule; possibly the
hens may lie hidden in the surrounding bushes, as is known to be the case
with the gray-hens in Scandinavia, and with other species in N. America.),
which afterwards pair with the victorious combatants. But in some cases
the pairing precedes instead of succeeding the combat: thus according to
Audubon (21. 'Ornithological Biography,' vol. ii. p. 275.), several males
of the Virginian goat-sucker (Caprimulgus virgianus) "court, in a highly
entertaining manner the female, and no sooner has she made her choice, than
her approved gives chase to all intruders, and drives them beyond his
dominions." Generally the males try to drive away or kill their rivals
before they pair. It does not, however, appear that the females invariably
prefer the victorious males. I have indeed been assured by Dr. W.
Kovalevsky that the female capercailzie sometimes steals away with a young
male who has not dared to enter the arena with the older cocks, in the same
manner as occasionally happens with the does of the red-deer in Scotland.
When two males contend in presence of a single female, the victor, no
doubt, commonly gains his desire; but some of these battles are caused by
wandering males trying to distract the peace of an already mated pair.
(22. Brehm, 'Thierleben,' etc., B. iv. 1867, p. 990. Audubon,
'Ornithological Biography,' vol. ii. p. 492.)
Even with the most pugnacious species it is probable that the pairing does
not depend exclusively on the mere strength and courage of the male; for
such males are generally decorated with various ornaments, which often
become more brilliant during the breeding-season, and which are sedulously
displayed before the females. The males also endeavour to charm or excite
their mates by love-notes, songs, and antics; and the courtship is, in many
instances, a prolonged affair. Hence it is not probable that the females
are indifferent to the charms of the opposite sex, or that they are
invariably compelled to yield to the victorious males. It is more probable
that the females are excited, either before or after the conflict, by
certain males, and thus unconsciously prefer them. In the case of Tetrao
umbellus, a good observer (23. 'Land and Water,' July 25, 1868, p. 14.)
goes so far as to believe that the battles of the male "are all a sham,
performed to show themselves to the greatest advantage before the admiring
females who assemble around; for I have never been able to find a maimed
hero, and seldom more than a broken feather." I shall have to recur to
this subject, but I may here add that with the Tetrao cupido of the United
States, about a score of males assemble at a particular spot, and,
strutting about, make the whole air resound with their extraordinary
noises. At the first answer from a female the males begin to fight
furiously, and the weaker give way; but then, according to Audubon, both
the victors and vanquished search for the female, so that the females must
either then exert a choice, or the battle must be renewed. So, again, with
one of the field-starlings of the United States (Sturnella ludoviciana) the
males engage in fierce conflicts, "but at the sight of a female they all
fly after her as if mad." (24. Audubon's 'Ornithological Biography;' on
Tetrao cupido, vol. ii. p. 492; on the Sturnus, vol. ii. p. 219.)
VOCAL AND INSTRUMENTAL MUSIC.
With birds the voice serves to express various emotions, such as distress,
fear, anger, triumph, or mere happiness. It is apparently sometimes used
to excite terror, as in the case of the hissing noise made by some
nestling-birds. Audubon (25. 'Ornithological Biography,' vol. v. p.
601.), relates that a night-heron (Ardea nycticorax, Linn.), which he kept
tame, used to hide itself when a cat approached, and then "suddenly start
up uttering one of the most frightful cries, apparently enjoying the cat's
alarm and flight." The common domestic cock clucks to the hen, and the hen
to her chickens, when a dainty morsel is found. The hen, when she has laid
an egg, "repeats the same note very often, and concludes with the sixth
above, which she holds for a longer time" (26. The Hon. Daines Barrington,
'Philosophical Transactions,' 1773, p. 252.); and thus she expresses her
joy. Some social birds apparently call to each other for aid; and as they
flit from tree to tree, the flock is kept together by chirp answering
chirp. During the nocturnal migrations of geese and other water-fowl,
sonorous clangs from the van may be heard in the darkness overhead,
answered by clangs in the rear. Certain cries serve as danger signals,
which, as the sportsman knows to his cost, are understood by the same
species and by others. The domestic cock crows, and the humming-bird
chirps, in triumph over a defeated rival. The true song, however, of most
birds and various strange cries are chiefly uttered during the breeding-
season, and serve as a charm, or merely as a call-note, to the other sex.
Naturalists are much divided with respect to the object of the singing of
birds. Few more careful observers ever lived than Montagu, and he
maintained that the "males of song-birds and of many others do not in
general search for the female, but, on the contrary, their business in the
spring is to perch on some conspicuous spot, breathing out their full and
armorous notes, which, by instinct, the female knows, and repairs to the
spot to choose her mate." (27. 'Ornithological Dictionary,' 1833, p.
475.) Mr. Jenner Weir informs me that this is certainly the case with the
nightingale. Bechstein, who kept birds during his whole life, asserts,
"that the female canary always chooses the best singer, and that in a state
of nature the female finch selects that male out of a hundred whose notes
please her most." (28. 'Naturgeschichte der Stubenvogel,' 1840, s. 4.
Mr. Harrison Weir likewise writes to me:--"I am informed that the best
singing males generally get a mate first, when they are bred in the same
room.") There can be no doubt that birds closely attend to each other's
song. Mr. Weir has told me of the case of a bullfinch which had been
taught to pipe a German waltz, and who was so good a performer that he cost
ten guineas; when this bird was first introduced into a room where other
birds were kept and he began to sing, all the others, consisting of about
twenty linnets and canaries, ranged themselves on the nearest side of their
cages, and listened with the greatest interest to the new performer. Many
naturalists believe that the singing of birds is almost exclusively "the
effect of rivalry and emulation," and not for the sake of charming their
mates. This was the opinion of Daines Barrington and White of Selborne,
who both especially attended to this subject. (29. 'Philosophical
Transactions,' 1773, p. 263. White's 'Natural History of Selborne,' 1825,
vol. i. p. 246.) Barrington, however, admits that "superiority in song
gives to birds an amazing ascendancy over others, as is well known to bird-
catchers."
It is certain that there is an intense degree of rivalry between the males
in their singing. Bird-fanciers match their birds to see which will sing
longest; and I was told by Mr. Yarrell that a first-rate bird will
sometimes sing till he drops down almost dead, or according to Bechstein
(30. 'Naturgesch. der Stubenvogel,' 1840, s. 252.), quite dead from
rupturing a vessel in the lungs. Whatever the cause may be, male birds, as
I hear from Mr. Weir, often die suddenly during the season of song. That
the habit of singing is sometimes quite independent of love is clear, for a
sterile, hybrid canary-bird has been described (31. Mr. Bold, 'Zoologist,'
1843-44, p. 659.) as singing whilst viewing itself in a mirror, and then
dashing at its own image; it likewise attacked with fury a female canary,
when put into the same cage. The jealousy excited by the act of singing is
constantly taken advantage of by bird-catchers; a male, in good song, is
hidden and protected, whilst a stuffed bird, surrounded by limed twigs, is
exposed to view. In this manner, as Mr. Weir informs me, a man has in the
course of a single day caught fifty, and in one instance, seventy, male
chaffinches. The power and inclination to sing differ so greatly with
birds that although the price of an ordinary male chaffinch is only
sixpence, Mr. Weir saw one bird for which the bird-catcher asked three
pounds; the test of a really good singer being that it will continue to
sing whilst the cage is swung round the owner's head.
That male birds should sing from emulation as well as for charming the
female, is not at all incompatible; and it might have been expected that
these two habits would have concurred, like those of display and pugnacity.
Some authors, however, argue that the song of the male cannot serve to
charm the female, because the females of some few species, such as of the
canary, robin, lark, and bullfinch, especially when in a state of
widowhood, as Bechstein remarks, pour forth fairly melodious strains. In
some of these cases the habit of singing may be in part attributed to the
females having been highly fed and confined (32. D. Barrington,
'Philosophical Transactions,' 1773, p. 262. Bechstein, 'Stubenvogel,'
1840, s. 4.), for this disturbs all the functions connected with the
reproduction of the species. Many instances have already been given of the
partial transference of secondary masculine characters to the female, so
that it is not at all surprising that the females of some species should
possess the power of song. It has also been argued, that the song of the
male cannot serve as a charm, because the males of certain species, for
instance of the robin, sing during the autumn. (33. This is likewise the
case with the water-ouzel; see Mr. Hepburn in the 'Zoologist,' 1845-46, p.
1068.) But nothing is more common than for animals to take pleasure in
practising whatever instinct they follow at other times for some real good.
How often do we see birds which fly easily, gliding and sailing through the
air obviously for pleasure? The cat plays with the captured mouse, and the
cormorant with the captured fish. The weaver-bird (Ploceus), when confined
in a cage, amuses itself by neatly weaving blades of grass between the
wires of its cage. Birds which habitually fight during the breeding-season
are generally ready to fight at all times; and the males of the
capercailzie sometimes hold their Balzen or leks at the usual place of
assemblage during the autumn. (34. L. Lloyd, 'Game Birds of Sweden,'
1867, p. 25.) Hence it is not at all surprising that male birds should
continue singing for their own amusement after the season for courtship is
over.
As shewn in a previous chapter, singing is to a certain extent an art, and
is much improved by practice. Birds can be taught various tunes, and even
the unmelodious sparrow has learnt to sing like a linnet. They acquire the
song of their foster parents (35. Barrington, ibid. p. 264, Bechstein,
ibid. s. 5.), and sometimes that of their neighbours. (36. Dureau de la
Malle gives a curious instance ('Annales des Sc. Nat.' 3rd series, Zoolog.,
tom. x. p. 118) of some wild blackbirds in his garden in Paris, which
naturally learnt a republican air from a caged bird.) All the common
songsters belong to the Order of Insessores, and their vocal organs are
much more complex than those of most other birds; yet it is a singular fact
that some of the Insessores, such as ravens, crows, and magpies, possess
the proper apparatus (37. Bishop, in 'Todd's Cyclopaedia of Anatomy and
Physiology,' vol. iv. p. 1496.), though they never sing, and do not
naturally modulate their voices to any great extent. Hunter asserts (38.
As stated by Barrington in 'Philosophical Transactions,' 1773, p. 262.)
that with the true songsters the muscles of the larynx are stronger in the
males than in the females; but with this slight exception there is no
difference in the vocal organs of the two sexes, although the males of most
species sing so much better and more continuously than the females.
It is remarkable that only small birds properly sing. The Australian genus
Menura, however, must be excepted; for the Menura Alberti, which is about
the size of a half-grown turkey, not only mocks other birds, but "its own
whistle is exceedingly beautiful and varied." The males congregate and
form "corroborying places," where they sing, raising and spreading their
tails like peacocks, and drooping their wings. (39. Gould, 'Handbook to
the Birds of Australia,' vol. i. 1865, pp. 308-310. See also Mr. T.W. Wood
in the 'Student,' April 1870, p. 125.) It is also remarkable that birds
which sing well are rarely decorated with brilliant colours or other
ornaments. Of our British birds, excepting the bullfinch and goldfinch,
the best songsters are plain-coloured. The kingfisher, bee-eater, roller,
hoopoe, woodpeckers, etc., utter harsh cries; and the brilliant birds of
the tropics are hardly ever songsters. (40. See remarks to this effect in
Gould's 'Introduction to the Trochilidae,' 1861, p. 22.) Hence bright
colours and the power of song seem to replace each other. We can perceive
that if the plumage did not vary in brightness, or if bright colours were
dangerous to the species, other means would be employed to charm the
females; and melody of voice offers one such means.
[Fig. 39. Tetrao cupido: male. (T.W. Wood.)]
In some birds the vocal organs differ greatly in the two sexes. In the
Tetrao cupido (Fig. 39) the male has two bare, orange-coloured sacks, one
on each side of the neck; and these are largely inflated when the male,
during the breeding-season, makes his curious hollow sound, audible at a
great distance. Audubon proved that the sound was intimately connected
with this apparatus (which reminds us of the air-sacks on each side of the
mouth of certain male frogs), for he found that the sound was much
diminished when one of the sacks of a tame bird was pricked, and when both
were pricked it was altogether stopped. The female has "a somewhat
similar, though smaller naked space of skin on the neck; but this is not
capable of inflation." (41. 'The Sportsman and Naturalist in Canada,' by
Major W. Ross King, 1866, pp. 144-146. Mr. T.W. Wood gives in the
'Student' (April 1870, p. 116) an excellent account of the attitude and
habits of this bird during its courtship. He states that the ear-tufts or
neck-plumes are erected, so that they meet over the crown of the head. See
his drawing, Fig. 39.) The male of another kind of grouse (Tetrao
urophasianus), whilst courting the female, has his "bare yellow oesophagus
inflated to a prodigious size, fully half as large as the body"; and he
then utters various grating, deep, hollow tones. With his neck-feathers
erect, his wings lowered, and buzzing on the ground, and his long pointed
tail spread out like a fan, he displays a variety of grotesque attitudes.
The oesophagus of the female is not in any way remarkable. (42.
Richardson, 'Fauna Bor. American: Birds,' 1831, p. 359. Audubon, ibid.
vol. iv. p. 507.)
[Fig. 40. The Umbrella-bird or Cephalopterus ornatus, male (from Brehm).]
It seems now well made out that the great throat pouch of the European male
bustard (Otis tarda), and of at least four other species, does not, as was
formerly supposed, serve to hold water, but is connected with the utterance
during the breeding-season of a peculiar sound resembling "oak." (43. The
following papers have been lately written on this subject: Prof. A.
Newton, in the 'Ibis,' 1862, p. 107; Dr. Cullen, ibid. 1865, p. 145; Mr.
Flower, in 'Proc. Zool. Soc.' 1865, p. 747; and Dr. Murie, in 'Proc. Zool.
Soc.' 1868, p. 471. In this latter paper an excellent figure is given of
the male Australian Bustard in full display with the sack distended. It is
a singular fact that the sack is not developed in all the males of the same
species.) A crow-like bird inhabiting South America (see Cephalopterus
ornatus, Fig. 40) is called the umbrella-bird, from its immense top knot,
formed of bare white quills surmounted by dark-blue plumes, which it can
elevate into a great dome no less than five inches in diameter, covering
the whole head. This bird has on its neck a long, thin, cylindrical fleshy
appendage, which is thickly clothed with scale-like blue feathers. It
probably serves in part as an ornament, but likewise as a resounding
apparatus; for Mr. Bates found that it is connected "with an unusual
development of the trachea and vocal organs." It is dilated when the bird
utters its singularly deep, loud and long sustained fluty note. The head-
crest and neck-appendage are rudimentary in the female. (44. Bates, 'The
Naturalist on the Amazons,' 1863, vol. ii. p. 284; Wallace, in
'Proceedings, Zoological Society,' 1850, p. 206. A new species, with a
still larger neck-appendage (C. penduliger), has lately been discovered,
see 'Ibis,' vol. i. p. 457.)
The vocal organs of various web-footed and wading birds are extraordinarily
complex, and differ to a certain extent in the two sexes. In some cases
the trachea is convoluted, like a French horn, and is deeply embedded in
the sternum. In the wild swan (Cygnus ferus) it is more deeply embedded in
the adult male than in the adult female or young male. In the male
Merganser the enlarged portion of the trachea is furnished with an
additional pair of muscles. (45. Bishop, in Todd's 'Cyclopaedia of
Anatomy and Physiology,' vol. iv. p. 1499.) In one of the ducks, however,
namely Anas punctata, the bony enlargement is only a little more developed
in the male than in the female. (46. Prof. Newton, 'Proc. Zoolog. Soc.'
1871, p. 651.) But the meaning of these differences in the trachea of the
two sexes of the Anatidae is not understood; for the male is not always the
more vociferous; thus with the common duck, the male hisses, whilst the
female utters a loud quack. (47. The spoonbill (Platalea) has its trachea
convoluted into a figure of eight, and yet this bird (Jerdon, 'Birds of
India,' vol. iii. p. 763) is mute; but Mr. Blyth informs me that the
convolutions are not constantly present, so that perhaps they are now
tending towards abortion.) In both sexes of one of the cranes (Grus virgo)
the trachea penetrates the sternum, but presents "certain sexual
modifications." In the male of the black stork there is also a well-marked
sexual difference in the length and curvature of the bronchi. (48.
'Elements of Comparative Anatomy,' by R. Wagner, Eng. translat. 1845, p.
111. With respect to the swan, as given above, Yarrell's 'History of
British Birds,' 2nd edition, 1845, vol. iii. p. 193.) Highly important
structures have, therefore, in these cases been modified according to sex.
It is often difficult to conjecture whether the many strange cries and
notes uttered by male birds during the breeding-season serve as a charm or
merely as a call to the female. The soft cooing of the turtle-dove and of
many pigeons, it may be presumed, pleases the female. When the female of
the wild turkey utters her call in the morning, the male answers by a note
which differs from the gobbling noise made, when with erected feathers,
rustling wings and distended wattles, he puffs and struts before her. (49.
C.L. Bonaparte, quoted in the 'Naturalist Library: Birds,' vol. xiv. p.
126.) The spel of the black-cock certainly serves as a call to the female,
for it has been known to bring four or five females from a distance to a
male under confinement; but as the black-cock continues his spel for hours
during successive days, and in the case of the capercailzie "with an agony
of passion," we are led to suppose that the females which are present are
thus charmed. (50. L. Lloyd, 'The Game Birds of Sweden,' etc., 1867, pp.
22, 81.) The voice of the common rook is known to alter during the
breeding-season, and is therefore in some way sexual. (51. Jenner,
'Philosophical Transactions,' 1824, p. 20.) But what shall we say about
the harsh screams of, for instance, some kinds of macaws; have these birds
as bad taste for musical sounds as they apparently have for colour, judging
by the inharmonious contrast of their bright yellow and blue plumage? It
is indeed possible that without any advantage being thus gained, the loud
voices of many male birds may be the result of the inherited effects of the
continued use of their vocal organs when excited by the strong passions of
love, jealousy and rage; but to this point we shall recur when we treat of
quadrupeds.
We have as yet spoken only of the voice, but the males of various birds
practise, during their courtship, what may be called instrumental music.
Peacocks and Birds of Paradise rattle their quills together. Turkey-cocks
scrape their wings against the ground, and some kinds of grouse thus
produce a buzzing sound. Another North American grouse, the Tetrao
umbellus, when with his tail erect, his ruffs displayed, "he shows off his
finery to the females, who lie hid in the neighbourhood," drums by rapidly
striking his wings together above his back, according to Mr. R. Haymond,
and not, as Audubon thought, by striking them against his sides. The sound
thus produced is compared by some to distant thunder, and by others to the
quick roll of a drum. The female never drums, "but flies directly to the
place where the male is thus engaged." The male of the Kalij-pheasant, in
the Himalayas, often makes a singular drumming noise with his wings, not
unlike the sound produced by shaking a stiff piece of cloth." On the west
coast of Africa the little black-weavers (Ploceus?) congregate in a small
party on the bushes round a small open space, and sing and glide through
the air with quivering wings, "which make a rapid whirring sound like a
child's rattle." One bird after another thus performs for hours together,
but only during the courting-season. At this season, and at no other time,
the males of certain night-jars (Caprimulgus) make a strange booming noise
with their wings. The various species of woodpeckers strike a sonorous
branch with their beaks, with so rapid a vibratory movement that "the head
appears to be in two places at once." The sound thus produced is audible
at a considerable distance but cannot be described; and I feel sure that
its source would never be conjectured by any one hearing it for the first
time. As this jarring sound is made chiefly during the breeding-season, it
has been considered as a love-song; but it is perhaps more strictly a love-
call. The female, when driven from her nest, has been observed thus to
call her mate, who answered in the same manner and soon appeared. Lastly,
the male hoopoe (Upupa epops) combines vocal and instrumental music; for
during the breeding-season this bird, as Mr. Swinhoe observed, first draws
in air, and then taps the end of its beak perpendicularly down against a
stone or the trunk of a tree, "when the breath being forced down the
tubular bill produces the correct sound." If the beak is not thus struck
against some object, the sound is quite different. Air is at the same time
swallowed, and the oesophagus thus becomes much swollen; and this probably
acts as a resonator, not only with the hoopoe, but with pigeons and other
birds. (52. For the foregoing facts see, on Birds of Paradise, Brehm,
'Thierleben,' Band iii. s. 325. On Grouse, Richardson, 'Fauna Bor.
Americ.: Birds,' pp. 343 and 359; Major W. Ross King, 'The Sportsman in
Canada,' 1866, p. 156; Mr. Haymond, in Prof. Cox's 'Geol. Survey of
Indiana,' p. 227; Audubon, 'American Ornitholog. Biograph.' vol. i. p. 216.
On the Kalij-pheasant, Jerdon, 'Birds of India,' vol. iii. p. 533. On the
Weavers, Livingstone's 'Expedition to the Zambesi,' 1865, p. 425. On
Woodpeckers, Macgillivray, 'Hist. of British Birds,' vol. iii. 1840, pp.
84, 88, 89, and 95. On the Hoopoe, Mr. Swinhoe, in 'Proc. Zoolog. Soc.'
June 23, 1863 and 1871, p. 348. On the Night-jar, Audubon, ibid. vol. ii.
p. 255, and 'American Naturalist,' 1873, p. 672. The English Night-jar
likewise makes in the spring a curious noise during its rapid flight.)
[Fig. 41. Outer tail-feather of Scolopax gallinago (from 'Proc. Zool.
Soc.' 1858).
Fig. 42. Outer tail-feather of Scolopax frenata.
Fig. 43. Outer tail-feather of Scolopax javensis.]
In the foregoing cases sounds are made by the aid of structures already
present and otherwise necessary; but in the following cases certain
feathers have been specially modified for the express purpose of producing
sounds. The drumming, bleating, neighing, or thundering noise (as
expressed by different observers) made by the common snipe (Scolopax
gallinago) must have surprised every one who has ever heard it. This bird,
during the pairing-season, flies to "perhaps a thousand feet in height,"
and after zig-zagging about for a time descends to the earth in a curved
line, with outspread tail and quivering pinions, and surprising velocity.
The sound is emitted only during this rapid descent. No one was able to
explain the cause until M. Meves observed that on each side of the tail the
outer feathers are peculiarly formed (Fig. 41), having a stiff sabre-shaped
shaft with the oblique barbs of unusual length, the outer webs being
strongly bound together. He found that by blowing on these feathers, or by
fastening them to a long thin stick and waving them rapidly through the
air, he could reproduce the drumming noise made by the living bird. Both
sexes are furnished with these feathers, but they are generally larger in
the male than in the female, and emit a deeper note. In some species, as
in S. frenata (Fig. 42), four feathers, and in S. javensis (Fig. 43), no
less than eight on each side of the tail are greatly modified. Different
tones are emitted by the feathers of the different species when waved
through the air; and the Scolopax Wilsonii of the United States makes a
switching noise whilst descending rapidly to the earth. (53. See M.
Meves' interesting paper in 'Proc. Zool. Soc.' 1858, p. 199. For the
habits of the snipe, Macgillivray, 'History of British Birds,' vol. iv. p.
371. For the American snipe, Capt. Blakiston, 'Ibis,' vol. v. 1863, p.
131.)
[Fig. 44. Primary wing-feather of a Humming-bird, the Selasphorus
platycercus (from a sketch by Mr. Salvin).
Upper figure, that of male;
lower figure, corresponding feather of female.]
In the male of the Chamaepetes un